Turn old baseball hats or painter's caps into new, stylish personalized hats of your own. The possibilities are endless.
What You'll Need:
Old baseball hat or painter's cap (available at paint supply stores)
Scrap of fabric
Scissors
Craft glue
Fabric paints
Paintbrush
Markers
Glitter
Sequins
How to Make Personalized Hats:
Step 1: Have an adult cut a circle or square from a scrap of fabric large enough to cover the front emblem of a baseball hat. Glue the fabric over the emblem.
Step 2: Decorate your hat with fabric paints and markers. Make your baseball hat into a fun beach cap. Paint an underwater ocean scene with fish and seaweed. Use the markers to add detail to the picture.
Step 3: Let the paint dry. Glue on glitter and sequins to make the fish sparkle.
Now that you know how to personalize hats, keep reading to learn how to style them.
Wild and Styled Hats
Wild and styled hats are so simple to create. Make a serious hat for parties, a silly hat just for laughs, or a theme hat to accompany a costume.
What You'll Need:
Wrapping paper
Scissors
Craft glue
Old paintbrush
Balloon or large ball
Trims such as feathers, ribbons, or rhinestones
How to Make Wild and Styled Hats:
Step 1: Cut two big identical circles out of wrapping paper.
Step 2: Mix equal parts of water and glue together. Using an old paintbrush, coat the wrong side of one piece of wrapping paper with glue. Place the other piece, wrong side down, over the glue.
Step 3: Place the paper on your head and form it into a hat shape while the glue is still wet. Once you've shaped the hat, place it over a blown-up balloon or a large ball.
Step 4: Let the hat set overnight. When it's dry, decorate it with feathers, ribbons, glitter, or rhinestones.
31.3.08
Book Blast Experiment
Compressed air has great strength. The book blast experiment is a science project that demonstrates just how powerful it can be.
What You'll Need:
3 books
Large airtight plastic bag
Step 1: Challenge a friend to move 3 books stacked on top of one another on a table by simply blowing at them. Of course, your friend won't be able to do it!
Step 2: Place a large plastic bag on the table, and put the 3 books on top of the bag. Leave the open end of the bag sticking out over the edge of the table.
Step 3: Hold the opening together, leaving a hole as small as possible. Blow into the bag. Take your time; stop to rest if you need to.
If you blow long and hard enough, the books will rise off the table. They will be supported by the compressed air in the plastic bag.
The next science project simulates a storm inside your own home. Keep reading science projects for kids: air pressure
What You'll Need:
3 books
Large airtight plastic bag
Step 1: Challenge a friend to move 3 books stacked on top of one another on a table by simply blowing at them. Of course, your friend won't be able to do it!
Step 2: Place a large plastic bag on the table, and put the 3 books on top of the bag. Leave the open end of the bag sticking out over the edge of the table.
Step 3: Hold the opening together, leaving a hole as small as possible. Blow into the bag. Take your time; stop to rest if you need to.
If you blow long and hard enough, the books will rise off the table. They will be supported by the compressed air in the plastic bag.
The next science project simulates a storm inside your own home. Keep reading science projects for kids: air pressure
Caved-in Can Experiment
Air pressure is strong enough to bend a can. Find out how you can amaze your friends with the caved-in can experiment.
What You'll Need:
Large container
Water
Ice cubes
Empty soda can
Measuring cup
Stove
Tongs or pot holders
Step 1: Fill a large container with water and ice cubes. Set it aside to use later.
Step 2: Pour 1/2 cup of water into an empty soda can.
Step 3: With adult supervision, put the can on a burner on the stove.
Step 4: When the water in the can starts to boil, you will see steam coming from the hole in the top of the can. Turn off the stove, and use tongs or pot holders to remove the can from the heat.
Step 5: Quickly put the can in the container of ice water, turning it upside down to rest on its top. Now, watch the can collapse as it cools.
What Happened? When you heated the water in the can, it produced steam that forced the air out of the can.
When you put the can in the ice water, its temperature lowered, and the steam condensed back into water.
The pressure of the air outside the can was greater than the air pressure inside the can. The weight of the outside air crushed the can.
What You'll Need:
Large container
Water
Ice cubes
Empty soda can
Measuring cup
Stove
Tongs or pot holders
Step 1: Fill a large container with water and ice cubes. Set it aside to use later.
Step 2: Pour 1/2 cup of water into an empty soda can.
Step 3: With adult supervision, put the can on a burner on the stove.
Step 4: When the water in the can starts to boil, you will see steam coming from the hole in the top of the can. Turn off the stove, and use tongs or pot holders to remove the can from the heat.
Step 5: Quickly put the can in the container of ice water, turning it upside down to rest on its top. Now, watch the can collapse as it cools.
What Happened? When you heated the water in the can, it produced steam that forced the air out of the can.
When you put the can in the ice water, its temperature lowered, and the steam condensed back into water.
The pressure of the air outside the can was greater than the air pressure inside the can. The weight of the outside air crushed the can.
Undoing Pollution
In Undoing Pollution, you'll learn how the effects of pollution are very difficult to erase. One of the most common forms is water pollution. In this activity, you'll have a chance to contaminate some water and then try to get rid of the pollution with different tools and devices.
What You'll Need:
Bucket
Water Pollutants (dirt, oil, trash)
Tongs
Strainer
Step 1: Fill a five-gallon bucket with clean water.
Step 2: Now, do your best to pollute the water. Throw in dirt, gravel, vegetable oil (to stand for toxic oil spills), trash (plastic packaging and any other kind of trash you've seen polluting water in nature), and other kinds of pollution. Yuck!
Step 3: Now, here's the hard part: What can you do to un-pollute the water? You can use tongs, strainers, and anything else you can think of. Can you get the water really clean again?
What You'll Need:
Bucket
Water Pollutants (dirt, oil, trash)
Tongs
Strainer
Step 1: Fill a five-gallon bucket with clean water.
Step 2: Now, do your best to pollute the water. Throw in dirt, gravel, vegetable oil (to stand for toxic oil spills), trash (plastic packaging and any other kind of trash you've seen polluting water in nature), and other kinds of pollution. Yuck!
Step 3: Now, here's the hard part: What can you do to un-pollute the water? You can use tongs, strainers, and anything else you can think of. Can you get the water really clean again?
Star Gazing
Star gazing is an easy way to teach yourself how to recognize the stars and constellations. Gather a few items, wait for a clear night, and you'll be ready for this science project for kids: the incredible universe.
What You'll Need:
Star chart
Clear night
Flashlight
Piece of red cellophane
Step 1: Get a star chart, and learn about the night sky. You can find one in many books at the library.
Step 2: On a clear night, go outdoors and see if you can find the constellations in the sky. The stars move throughout the year, so you'll see different constellations at different times of year.
Step 3: Look for the starting point for star-gazing, usually the North Star, also called Polaris. It's the only star that does not move. To find the North Star, find the Little Dipper. The last star on its handle is the North Star. Another way to find the North Star is to locate the Big Dipper and trace an imaginary line from the two stars in the dipper's front edge, leading up from the dipper. The North Star is along this line.
Step 4: Once you've found the North Star, try to locate the other constellations. Use a flashlight to refer to your star chart. (Cover the flashlight with red cellophane so you can still see the stars when you look back up at the sky.)
Keep reading on the next page to find out how you can fill your umbrella with constellations.
Umbrella Full of Constellations
Create your own private planetarium with an umbrella full of constellations. Find them, mark them, and save them to look at again another day. Have fun with this science project for kids: the incredible universe.
What You'll Need:
Clear night when the moon is invisible or very small
Black umbrella (that it's OK to mark up with chalk)
White chalk
Star chart
Step 1: Open the umbrella, and hold it over your head.
Step 2: Point the tip of the umbrella at the North Star. (Use a star chart to find the North Star.)
Step 3: Look up at the underside of the umbrella. You may see the stars shining through.
Step 4: Use white chalk to mark on the umbrella each place where you see a star. (This will be easier if someone else holds the umbrella for you.) If you can't see the stars through the umbrella, just look in the sky and mark the stars in the same positions as you see them in the sky.
Step 5: When you've marked all the stars you can see, take the umbrella inside. Compare your marks to a star chart. What stars and constellations did you mark?
Step 6: Draw lines connecting the constellations, and label them with their names.
Go to the next page to find out how you can turn constellation punch-outs into a star theater.
Star Theater
You'll be the star when you learn the shapes of some constellations and put on a show for the family with this star theater!
What You'll Need:
Empty steel cans (such as soup or coffee cans)
Pliers
Tracing paper
Book of constellations
Pen
Scissors
Pin
Masking tape
Hammer
Thin finishing nail
Flashlight
Black cloth (optional)
Step 1: Clean the cans, and use pliers to flatten any sharp points.
Step 2: Lay the end of the can on the tracing paper, and draw circles with a pencil.
Step 3: Lay the marked tracing paper on a picture of a constellation in a book, and trace a constellation inside of each circle, using dots to represent stars. If a constellation won't fit in the circle, you can try drawing it free hand.
Step 4: Cut out the circles, and use a pin to poke a hole where each star is marked.
Step 5: Turn each circle over so the constellation is backward, and tape one to the closed end of the steel can.
Step 6: Use a hammer and a thin finishing nail to punch a hole through each pin hole. (Always be careful when using a hammer!) Remove the paper.
Step 7: Write the name of each constellation on a piece of masking tape, and attach each piece of masking tape to the can it represents. This is so you can remember which constellation is which.
Step 8: Shine a flashlight into the open end of the can to shine the constellation on the ceiling. You can shroud the open end of the can in black cloth to shut out excess light when you put on a star show for your family.
Have you ever wondered how big the solar system is? Go to the next page of science projects for kids: the incredible universe to find out by making a scale model with peas, fruits and nuts.
What You'll Need:
Star chart
Clear night
Flashlight
Piece of red cellophane
Step 1: Get a star chart, and learn about the night sky. You can find one in many books at the library.
Step 2: On a clear night, go outdoors and see if you can find the constellations in the sky. The stars move throughout the year, so you'll see different constellations at different times of year.
Step 3: Look for the starting point for star-gazing, usually the North Star, also called Polaris. It's the only star that does not move. To find the North Star, find the Little Dipper. The last star on its handle is the North Star. Another way to find the North Star is to locate the Big Dipper and trace an imaginary line from the two stars in the dipper's front edge, leading up from the dipper. The North Star is along this line.
Step 4: Once you've found the North Star, try to locate the other constellations. Use a flashlight to refer to your star chart. (Cover the flashlight with red cellophane so you can still see the stars when you look back up at the sky.)
Keep reading on the next page to find out how you can fill your umbrella with constellations.
Umbrella Full of Constellations
Create your own private planetarium with an umbrella full of constellations. Find them, mark them, and save them to look at again another day. Have fun with this science project for kids: the incredible universe.
What You'll Need:
Clear night when the moon is invisible or very small
Black umbrella (that it's OK to mark up with chalk)
White chalk
Star chart
Step 1: Open the umbrella, and hold it over your head.
Step 2: Point the tip of the umbrella at the North Star. (Use a star chart to find the North Star.)
Step 3: Look up at the underside of the umbrella. You may see the stars shining through.
Step 4: Use white chalk to mark on the umbrella each place where you see a star. (This will be easier if someone else holds the umbrella for you.) If you can't see the stars through the umbrella, just look in the sky and mark the stars in the same positions as you see them in the sky.
Step 5: When you've marked all the stars you can see, take the umbrella inside. Compare your marks to a star chart. What stars and constellations did you mark?
Step 6: Draw lines connecting the constellations, and label them with their names.
Go to the next page to find out how you can turn constellation punch-outs into a star theater.
Star Theater
You'll be the star when you learn the shapes of some constellations and put on a show for the family with this star theater!
What You'll Need:
Empty steel cans (such as soup or coffee cans)
Pliers
Tracing paper
Book of constellations
Pen
Scissors
Pin
Masking tape
Hammer
Thin finishing nail
Flashlight
Black cloth (optional)
Step 1: Clean the cans, and use pliers to flatten any sharp points.
Step 2: Lay the end of the can on the tracing paper, and draw circles with a pencil.
Step 3: Lay the marked tracing paper on a picture of a constellation in a book, and trace a constellation inside of each circle, using dots to represent stars. If a constellation won't fit in the circle, you can try drawing it free hand.
Step 4: Cut out the circles, and use a pin to poke a hole where each star is marked.
Step 5: Turn each circle over so the constellation is backward, and tape one to the closed end of the steel can.
Step 6: Use a hammer and a thin finishing nail to punch a hole through each pin hole. (Always be careful when using a hammer!) Remove the paper.
Step 7: Write the name of each constellation on a piece of masking tape, and attach each piece of masking tape to the can it represents. This is so you can remember which constellation is which.
Step 8: Shine a flashlight into the open end of the can to shine the constellation on the ceiling. You can shroud the open end of the can in black cloth to shut out excess light when you put on a star show for your family.
Have you ever wondered how big the solar system is? Go to the next page of science projects for kids: the incredible universe to find out by making a scale model with peas, fruits and nuts.
Make a Planetarium
Make a planetarium, and you can create a representations of the night sky in your house. You'll find simple instructions in this science project for kids: the incredible universe.
What You'll Need:
Shoe box
Scissors
Star chart
Pen or pencil
Pin
Tape
Flashlight
Books
Step 1: On one end of a shoe box, cut a hole just big enough for a flashlight to fit into.
Step 2: Cut a rectangle out of the other end of the shoe box.
Step 3: Using the star guide, draw dots on a piece of paper to represent the stars of a constellation, and poke holes through the dots with a pin. Do this for several different constellations.
Step 4: Put one of the sheets of paper over the rectangular hole in the box, and tape it in place.
Step 5: Support the flashlight with a stack of books, and put it into the hole in the other end of the box.
Step 6: In a darkened room, turn on the flashlight, and project your constellation onto a wall. Quiz your friends or family to see if they can identify the different constellations.
What You'll Need:
Shoe box
Scissors
Star chart
Pen or pencil
Pin
Tape
Flashlight
Books
Step 1: On one end of a shoe box, cut a hole just big enough for a flashlight to fit into.
Step 2: Cut a rectangle out of the other end of the shoe box.
Step 3: Using the star guide, draw dots on a piece of paper to represent the stars of a constellation, and poke holes through the dots with a pin. Do this for several different constellations.
Step 4: Put one of the sheets of paper over the rectangular hole in the box, and tape it in place.
Step 5: Support the flashlight with a stack of books, and put it into the hole in the other end of the box.
Step 6: In a darkened room, turn on the flashlight, and project your constellation onto a wall. Quiz your friends or family to see if they can identify the different constellations.
Make a Kaleidoscope
A kaleidoscope is an ideal science project that teaches kids how to reflect the spectrum of colors and make beautiful images. In a kaleidoscope, mirrors reflect multiple images off of one another.
What You'll Need:
3 small mirrors of the same size
Tape
Waxed paper
Pencil
Scissors
Construction paper
How to Make a Kaleidoscope:
Step 1: To make a kaleidoscope, tape together 3 small mirrors in a triangle shape with the mirror-sides facing inward.
Step 2: Stand the mirrors up on a piece of waxed paper, and trace around the bottom of the mirrors. Cut out this triangle shape, and then tape the piece of waxed paper in place at the bottom of the 3 mirrors.
Step 3: Cut out many small pieces and shapes from colored sheets of construction paper, and drop them inside the mirrors.
Step 4: Give your kaleidoscope a shake, then look inside. You will see some interesting patterns. The mirrors will reflect interesting shapes and colors.
Help kids Discover Hidden Leaf Colors while participating in this innovative science project. Find out how to bring fall colors out of spring leaves on the next page of science projects for kids: spectrum of colors
What You'll Need:
3 small mirrors of the same size
Tape
Waxed paper
Pencil
Scissors
Construction paper
How to Make a Kaleidoscope:
Step 1: To make a kaleidoscope, tape together 3 small mirrors in a triangle shape with the mirror-sides facing inward.
Step 2: Stand the mirrors up on a piece of waxed paper, and trace around the bottom of the mirrors. Cut out this triangle shape, and then tape the piece of waxed paper in place at the bottom of the 3 mirrors.
Step 3: Cut out many small pieces and shapes from colored sheets of construction paper, and drop them inside the mirrors.
Step 4: Give your kaleidoscope a shake, then look inside. You will see some interesting patterns. The mirrors will reflect interesting shapes and colors.
Help kids Discover Hidden Leaf Colors while participating in this innovative science project. Find out how to bring fall colors out of spring leaves on the next page of science projects for kids: spectrum of colors
Bottle Music
Bottle music is a science project for kids on producing sound that explores how volume and liquid affect sound waves. After experimenting with different types of bottles and levels of water, show your friends how this project works and start a bottle music band!
What You'll Need:
Eight empty bottles
Water
Step 1: Stand eight empty bottles side by side on a table in front of you. Fill the bottle on the left about 1/4 of the way full with water.
Step 2: Add water to the next bottle so that the water level is a bit higher than in the first bottle. Continue adding water to the bottles so that each one has a little bit more water in it than the bottle to its left.
Step 3: Blow across the bottle on the left, and you'll hear a low note. Blow across the bottle on the right, and you'll hear a high note. By adjusting the amount of water in each bottle, you can produce a whole musical scale.
When you blow across the bottle, you cause the air inside to vibrate, which produces a sound. The amount of air in the bottle affects the sound it makes. The bottles with more air produce low sounds, and the bottles with less air produce high sounds.
Sound Barriers
You don't need to be a super hero to stop sound. This sound barriers science project for kids shows how easy it is to halt sound waves in their tracks.
What You'll Need:
A friend
Step 1: Go into your backyard and stand about as far from your partner as your house is wide. (That should be about 30 feet or so.) Try to talk to one another.
As long as there is nothing between you and your partner, you should be able to hear one another fairly well, though you may have to raise your voice a little.
Step 2: Now stand on one side of a house while your partner stands on the other side. Try to shout something to your partner and see if you can be heard clearly. Have your partner shout something at you.
You may have heard something, but perhaps you could not make out what your partner was saying. Was the sound weak and distorted?
Try the same experiment with a wall between you and your partner. Try it with a fence, a window, a blanket, and other types of barriers. Does the thickness of the barrier matter?
What You'll Need:
Eight empty bottles
Water
Step 1: Stand eight empty bottles side by side on a table in front of you. Fill the bottle on the left about 1/4 of the way full with water.
Step 2: Add water to the next bottle so that the water level is a bit higher than in the first bottle. Continue adding water to the bottles so that each one has a little bit more water in it than the bottle to its left.
Step 3: Blow across the bottle on the left, and you'll hear a low note. Blow across the bottle on the right, and you'll hear a high note. By adjusting the amount of water in each bottle, you can produce a whole musical scale.
When you blow across the bottle, you cause the air inside to vibrate, which produces a sound. The amount of air in the bottle affects the sound it makes. The bottles with more air produce low sounds, and the bottles with less air produce high sounds.
Sound Barriers
You don't need to be a super hero to stop sound. This sound barriers science project for kids shows how easy it is to halt sound waves in their tracks.
What You'll Need:
A friend
Step 1: Go into your backyard and stand about as far from your partner as your house is wide. (That should be about 30 feet or so.) Try to talk to one another.
As long as there is nothing between you and your partner, you should be able to hear one another fairly well, though you may have to raise your voice a little.
Step 2: Now stand on one side of a house while your partner stands on the other side. Try to shout something to your partner and see if you can be heard clearly. Have your partner shout something at you.
You may have heard something, but perhaps you could not make out what your partner was saying. Was the sound weak and distorted?
Try the same experiment with a wall between you and your partner. Try it with a fence, a window, a blanket, and other types of barriers. Does the thickness of the barrier matter?
29.3.08
Handmade Leaf and Twig Diary
Your child's private diary is even more personal when she creates it herself in this artistic kids' paper craft. With a handmade paper cover, kids will be so proud of their work they'll have a hard time hiding their journals away from prying eyes!
What You'll Need:
Diary Cover
5x7-inch wooden picture frame
8x10-inch coarse nylon net
Large brown paper grocery bag
Newspapers
21-inch square of old sheet
20x20-inch piece of flat, smooth, nonporous plastic or similar material
Tools: Staple gun, two 1-gallon buckets, large slotted spoon, blender, deep plastic dishpan, kitchen sponge, clothespins, and clothesline
Diary
15-20 pieces of recycled paper, 5x7 inches
4-inch twig
12 inches of twine
1 piece each of heavy gold, orange, and dark red paper, 5 inches square
Tools: Pencil, tracing paper, hole punch, scissors, and craft glue
How to Make a Handmade Leaf and Twig Diary:
Step 1: Staple the nylon net across the back of the picture frame, stretching the net tightly (this is best done by an adult). Set aside.
Step 2: Fill a bucket half full of warm water. Tear the grocery bag into 2x2-inch pieces. Drop the pieces into the bucket of water and stir with the slotted spoon. Let soak 1/2 hour.
Step 3: In the blender jar, add the soaked paper to an equal amount of water a little at a time. Don't overload blender and use plenty of water.
Blend on low speed, then medium speed, until paper becomes pulpy. Don't overblend. Fill dishpan halfway with warm water. Pour pulp into pan.
How to Make a Handmade Leaf and Twig Diary:
Step 1: Staple the nylon net across the back of the picture frame, stretching the net tightly (this is best done by an adult). Set aside.
Step 2: Fill a bucket half full of warm water. Tear the grocery bag into 2x2-inch pieces. Drop the pieces into the bucket of water and stir with the slotted spoon. Let soak 1/2 hour.
Step 3: In the blender jar, add the soaked paper to an equal amount of water a little at a time. Don't overload blender and use plenty of water.
Blend on low speed, then medium speed, until paper becomes pulpy. Don't overblend. Fill dishpan halfway with warm water. Pour pulp into pan.
Step 4: Hold the frame horizontally, net side up. As you lower it into the pan of pulp, tilt it down and scoop under the pulp, moving it away from your body. Tilt it to horizontal under the water and lift up, shaking it slightly.
Do this in one smooth, continuous motion. If the pulp is too lumpy or has holes, dump it back into the pan and start over.
Step 5: Let the pulp on the frame drain for a moment over the pan. Wet one of the pieces of sheet and smooth it onto the flat plastic, removing any air bubbles. It is important that the sheet be flat and stuck to the surface; if not, the pulp will not come off the netting later.
Turn the frame with the pulp upside down and set it onto the wet sheet. Use the sponge to press out as much water as possible. Do not rub.
Step 6: When most of the water has been removed, lift the frame away from the pulp. The pulp should stick to the sheet. If it does not stick, or if there are holes, dump it back into the pan of pulp and start over.
Step 7: Once the pulp is stuck to the sheet, pin the sheet to the clothesline until the piece of paper on it is dry, then carefully peel away the paper. While the paper dries, make another piece.
Step 8: On a piece of handmade paper, measure 1/2 inch in from a short edge and make a light pencil line. Then measure up from a long edge and make marks at 1-1/2 and 3-1/2 inches.
Punch holes at the marks. Using this sheet as a guide, mark and punch holes in recycled paper and other sheet of handmade paper. Stack all sheets, with the handmade paper on the top and bottom.
Step 9: Thread the twine up through each hole. Lay the twig over the holes and wrap twine around the twig. Then wrap twine around the opposite end of the twig and tie the ends in the middle. Set aside.
Step 10: Draw the leaves and cut them out. Trace an oak leaf on the dark red paper and elm leaves on the gold and orange papers. Cut out. Glue leaves onto front of book. Press under a heavy book and let dry.
What You'll Need:
Diary Cover
5x7-inch wooden picture frame
8x10-inch coarse nylon net
Large brown paper grocery bag
Newspapers
21-inch square of old sheet
20x20-inch piece of flat, smooth, nonporous plastic or similar material
Tools: Staple gun, two 1-gallon buckets, large slotted spoon, blender, deep plastic dishpan, kitchen sponge, clothespins, and clothesline
Diary
15-20 pieces of recycled paper, 5x7 inches
4-inch twig
12 inches of twine
1 piece each of heavy gold, orange, and dark red paper, 5 inches square
Tools: Pencil, tracing paper, hole punch, scissors, and craft glue
How to Make a Handmade Leaf and Twig Diary:
Step 1: Staple the nylon net across the back of the picture frame, stretching the net tightly (this is best done by an adult). Set aside.
Step 2: Fill a bucket half full of warm water. Tear the grocery bag into 2x2-inch pieces. Drop the pieces into the bucket of water and stir with the slotted spoon. Let soak 1/2 hour.
Step 3: In the blender jar, add the soaked paper to an equal amount of water a little at a time. Don't overload blender and use plenty of water.
Blend on low speed, then medium speed, until paper becomes pulpy. Don't overblend. Fill dishpan halfway with warm water. Pour pulp into pan.
How to Make a Handmade Leaf and Twig Diary:
Step 1: Staple the nylon net across the back of the picture frame, stretching the net tightly (this is best done by an adult). Set aside.
Step 2: Fill a bucket half full of warm water. Tear the grocery bag into 2x2-inch pieces. Drop the pieces into the bucket of water and stir with the slotted spoon. Let soak 1/2 hour.
Step 3: In the blender jar, add the soaked paper to an equal amount of water a little at a time. Don't overload blender and use plenty of water.
Blend on low speed, then medium speed, until paper becomes pulpy. Don't overblend. Fill dishpan halfway with warm water. Pour pulp into pan.
Step 4: Hold the frame horizontally, net side up. As you lower it into the pan of pulp, tilt it down and scoop under the pulp, moving it away from your body. Tilt it to horizontal under the water and lift up, shaking it slightly.
Do this in one smooth, continuous motion. If the pulp is too lumpy or has holes, dump it back into the pan and start over.
Step 5: Let the pulp on the frame drain for a moment over the pan. Wet one of the pieces of sheet and smooth it onto the flat plastic, removing any air bubbles. It is important that the sheet be flat and stuck to the surface; if not, the pulp will not come off the netting later.
Turn the frame with the pulp upside down and set it onto the wet sheet. Use the sponge to press out as much water as possible. Do not rub.
Step 6: When most of the water has been removed, lift the frame away from the pulp. The pulp should stick to the sheet. If it does not stick, or if there are holes, dump it back into the pan of pulp and start over.
Step 7: Once the pulp is stuck to the sheet, pin the sheet to the clothesline until the piece of paper on it is dry, then carefully peel away the paper. While the paper dries, make another piece.
Step 8: On a piece of handmade paper, measure 1/2 inch in from a short edge and make a light pencil line. Then measure up from a long edge and make marks at 1-1/2 and 3-1/2 inches.
Punch holes at the marks. Using this sheet as a guide, mark and punch holes in recycled paper and other sheet of handmade paper. Stack all sheets, with the handmade paper on the top and bottom.
Step 9: Thread the twine up through each hole. Lay the twig over the holes and wrap twine around the twig. Then wrap twine around the opposite end of the twig and tie the ends in the middle. Set aside.
Step 10: Draw the leaves and cut them out. Trace an oak leaf on the dark red paper and elm leaves on the gold and orange papers. Cut out. Glue leaves onto front of book. Press under a heavy book and let dry.
How to Make Holiday Bag Crafts for Kids
Crafting a holiday bag is not just for the winter season. A bonny-bright basket is the perfect craft to help celebrate the springtime holidays. It's super-quick and easy to create, and it's just the thing to fill with goodies or little treasures.
Some parts of this craft may be difficult for small hands, so kids will want an adult to help.
What You'll Need
Yellow paper bag, 4-3/4 inches wide
Assorted stickers
Pencil
Ruler
Scissors
Craft glue
How to Make a Bonny-Bright Basket
Step 1: With the bag flat on your work surface, measure and cut 3 inches off the top. Set this piece aside.
Step 2: Open the bottom of the bag. Fold 1 inch of the top edge down into the inside of the bag; repeat to create the basket base.
Step 3: Using the piece you set aside in step 1, fold in 1 inch lengthwise on both sides. Glue these sides together to create a 1-inch-wide strip (for the handle).
Step 4: Measure 2-1/2 inches from one end of the handle, and fold at this line. Glue the folded end centered in the bottom of the basket. Glue the next 2-1/2 inches of the handle up the side of the basket. Loop the handle over to the other side of the basket, and pull down until the end of the handle meets the strip at the bottom. Glue the handle in place on the second side of the basket.
Step 5: Decorate the outside of the basket and the handle with stickers.
How Breast Implants Work
In 2003, plastic surgeons performed 280,401 breast-augmentation surgeries in the United States. This made breast augmentation the second most common elective surgery and the most common type of breast surgery for that year. Breast augmentation, or augmentation mammoplasty, is the insertion of breast implants into a woman's breasts to increase their size. These implants have been the center of controversy for almost 30 years.
In this article, HowStuffWorks looks at breast implants and the surgery that inserts them into a woman's breasts. We'll examine the history and controversy surrounding breast implants and the risks associated with them, describe the various methods used to implant them, and learn how men also use breast surgeries to alter their appearance.
Anatomy of a Breast
In order to understand how breast implants work, it helps to understand the structure of the breast. Breasts are tear-shaped, milk-producing glands that cover a woman's pectoral muscles and are suspended over the rib cage. They are held in place by supporting ligaments and muscles.
The structure of the breast is divided into two functional components: the epithelial component (the system that produces milk) and the structural component (the system of fatty tissue and ligaments that support and protect the structure of the breast).
The epithelial component is comprised of a series of 15 to 25 lobes arranged in an orderly fashion around the center of the breast (imagine the petals of a flower). Each lobe contains clusters of lobules that resemble clusters of grapes. All of the lobules end in dozens of tiny milk producing bulbs. The lobes all connect to a network of ducts called the lactiferous sinus, which carries milk to the nipple. The nipple is surrounded by the areola -- the dark, circular tissue that crowns the outside of the breast. The lactiferous sinus carries the milk through the nipple and out of the breast.
The structural component of the breast is comprised mostly of a fatty tissue called adipose. There is no muscle in the actual breast, but there are a series of muscles behind and underneath the breasts. These muscles work in conjunction with a ligament called Cooper's ligament, and together they act like a natural bra, supporting the weight of the breasts on the front of a woman's body.
The size and shape of a woman's breasts are primarily determined by hereditary. Other factors that can affect breast size (outside of traumas and cancer) include fluctuating weight, medications, pregnancy, menstruation, and menopause.
Bra Size
Breast size is generally (but not scientifically) measured by bra size. In the United States, bras are measured with a combination of:
the diameter in inches around a woman's rib cage just under her breasts
a letter that indicates the size of the cup that actually holds the breast
Cup sizes can be AA, A, B, C, D, DD and beyond, with AA as the smallest. So a typical bra size might be "34B."
Breast Implant Basics
Breast implants are small, medical-grade sacs comprised of an elastomer shell with a self-sealing filling valve located on either the front or back. Breast implants are filled with silicone gel or a sterile saline solution (salt water).
Some implants are pre-filled, but most are filled after surgery. It's this filling that blows the implant up like a water balloon to increase breast size. Saline implants are the most common type of implant used today due to the FDA's ban on the use of silicone breast implants in the United States in 1992 (although silicone implants are still available in certain circumstances -- see the Controversy section).
Breast implants come in a variety of shapes and sizes. The size of breast implants is measured in cubic centimeters (ccs), and they increase the size of a woman's breasts one cup size every 175 to 200 ccs
Generally, implants come in three sizes, and the size of the implant that is used depends on the patient's desired outcome and the size breasts that their physical frame can support. Choosing a breast implant that is too large can cause surgical complications or make the implant visible through the skin after the surgery.
Implant Shape
Size is not the only issue to consider when discussing implants. To get the safest and most natural-looking results, breast implants are made with a variety of features in mind. The first of these features is shape. Breast implants come in two shapes: round and contoured.
Round implants are the most common type of implant used. Many women choose round implants because they tend to provide the greatest amount of lift, fullness and cleavage. Some women, however, find the round implants too fake looking and opt for more natural-looking alternatives.
Contoured implants have a more tear-drop shape to mimic the anatomical shape of the breasts. Contoured implants were originally developed for breast reconstruction but have become quite popular in augmentation surgery for women who want a more natural shape. The best shape for the job is usually worked out between the surgeon and patient, and the variables they consider are:
The amount of tissue the surgeon has to work with
The patient's anatomy
Where the surgeon places the implant in the breast
The thing to bear in mind is that the placement of the implant has a far greater effect on the final look of the augmentation than the shape of the implant.
String Implants
String breast implants, or polypropylene implants, were developed by Dr. Gerald W. Johnson and designed to yield extreme, almost cartoonish breast sizes. The polypropylene in string breast implants absorbs fluids and expands once implanted into the breast. The result is almost continuous breast growth after surgery. Despite the apparent danger and frequent complications, this type of breast implant was popular among adult entertainers. String implants were only available for a very short time before being pulled off the shelves by the FDA several years ago.
Implant Texture
A capsule of scar tissue forms around the implant after surgery. This is a natural reaction of the body to protect itself from the introduction of a foreign object. The formation of this scar capsule is called capsular contracture. In extreme cases, this scar capsule will result in a hardening of the breasts, which may be painful and requires additional surgery.
Textured breast implants were created to reduce the chance of capsular contracture. The textured surface of these implants allows the scar tissue to adhere to the implant, hopefully decreasing the amount of scar tissue that grows. In addition, the implant sticking to the scar capsule prevents it from moving around inside the breast. It is still debatable whether or not textured implants actually reduce the instances of capsular contracture; but evidence does indicate that textured implants have a greater tendency to rupture.
Smooth breast implants move around freely inside of the capsule. This freedom can create a more natural movement in the overall breast; however, depending on the placement of the implant, it can sometimes create an undesirable side effect known as rippling (see the Risks section). There are many variables that affect rippling, and the surgeon will guide the patient toward the implant texture for her anatomy.
Expandables
A less commonly used type of implant is the Spectrum Expandable saline implant. This implant has a three-part system consisting of the Becker valve, fill tube, and reservoir system. An expandable implant can have saline added or removed in 50 cc increments using a fill port that is surgically implanted into the patient's armpit, allowing for minimally invasive post-operative adjustment.
The fill port is attached to a tube that directs saline to and from the implant reservoir. Once the patient is happy with the size and final look of the implants, a minor procedure removes the fill port and tube. A three-part seal made up of a kink valve, leaf valve, and the plug on the implant closes the valve without a need for additional surgery. Unlike normal implants, once the valve on an expandable implant is closed, it cannot be reopened; this creates the disadvantage that if it needs to be removed in a revision surgery, it must be removed without being drained, which requires a much larger incision.
Implant Placement
One of the most important factors in a successful breast augmentation is the proper placement of the implant. There are three places implants can be put to increase the size of a woman's breasts:
Subglandular
Subpectoral
Submuscular
Subglandular placement puts the implant directly behind the mammary gland and in front of the muscle. This placement requires the least complicated surgery and yields the quickest recovery. Athletic women may opt for this placement because it prevents flexing chest muscles from interfering with the look or integrity of the implant
The downsides of this placement are increased chance for capsular contracture, greater visibility and vulnerability for the implant. This is because only the flesh and gland separate the implant from the outside world. Depending on the amount of available breast tissue, the implant may be seen "rippling" through the skin.
Subpectoral placement involves lodging the implant under the pectoralis major muscle. Because of the structure of this muscle, the implant is only partially covered. This alternative reduces the risk of capsular contracture and visible implant rippling, but recovery time from this positioning is typically longer and more painful because the doctor has to manipulate the muscle during surgery. Also, because of increased swelling, the implant may take longer to drop into a natural position after surgery
If the augmentation is being performed to lift sagging breasts, this type of placement may not be the right approach. Because the implant is only partially covered by the muscle, the weight of the fluid is not supported. In a woman with sagging breasts, the implant may droop and create two separate bulges in the breast lobe.
Submuscular placement puts the implant firmly behind the chest muscle wall. The implant is placed behind the pectoralis major muscle and behind all of the supporting fascia (connective tissue) and non-pectoral muscle groups. Submuscular implants tend to be the best for mammograms, as they put the implant fully behind the area that needs to be examined. This placement has the same drawbacks of subpectoral placement with an even longer recovery time.
Procedure
Plastikos
For most people, the word "plastic" in "plastic surgery" seems imply fakery. In fact, the word plastic is derived from the Greek word plastikos, which means "to mold or shape," which is exactly what plastic surgeons do. For either cosmetic reasons or reconstruction, plastic surgeons mold or reshape tissue and materials to build or rebuild a part of the human body. Plastic surgery encompasses both elective cosmetic surgery and reconstructive procedures.
Depending on the patient and the desired outcome, breast augmentation surgery can be a very simple or very complex procedure.
After pre-operative preparation, the surgery starts by cutting one incision into the patient for each implant. The incisions are small and placed so that the scarring is minimal and hard to see. Once the incision is created, the surgeon must cut a path through the tissue to the final destination of the implant. Once that path has been created, the tissue and/or muscle (depending on placement) must be separated to create a pocket for the implant. This is where the surgeon's skill really comes into play: When deciding where to cut the pocket in the breast, the surgeon must predict what the breasts will look like once the implants are filled. In more extreme augmentation surgeries, this involves repositioning the nipple, adjusting for cleavage and creating a new crease under the breast.
In some cases, augmentation surgery is accompanied by mastopexy (breast lift) surgery so that everything ends up in the right place. To aid in positioning, the surgeon may decide to use a sizer or disposable implant. Sizers are temporary implants attached to a tube that the surgeon can work inside the pocket and fill up to test placement, implant size and fill levels. Once this has been tested, the sizer is removed and replaced with the permanent implant.
When inflatable implants are used, they are rolled up like a cigar and pushed into the incision, through the channel and into place. This is true no matter which type of incision is used (we'll talk about incisions in the following sections). Once the implant is positioned, the incision is closed. In the last step, the surgeon uses a syringe to fill the implant with saline through the valve, filling it to the predetermined size.
If the patient has opted to use pre-filled implants, the incision will be larger. Inserting textured, pre-filled implants requires the longest incision, providing more room for inserting an implant with a rough shell and for manipulating the less-pliable implant once it's in place.
Plastic surgeons can use one of four different types of incisions to insert the implant into the breast: peri-areolar, inframammary fold, transaxillary, and TUBA. In the next sections, we will learn the difference between these types of incision.
Peri-areolar Incision
The peri-areolar incision, or nipple incision, is one of the most commonly used incisions in breast augmentation surgery. The nipple incision allows sub-glandular, sub-pectoral, or sub-muscular placement of the implant. The implant can be both inserted and removed through the nipple incision in the event of complications.
The incision is made where the darker skin of the areola meets the lighter skin of the breast. This allows the scar to blend in with the natural change in flesh pigment. The implant is rolled up into a protective sleeve before being inserted. The sleeve prevents the implant from coming into contact with bacteria in the lactiferous sinus, which could cause germ contamination after the surgery. After placement, the sleeve is removed.
One of the greatest advantages of this type of incision is that the surgeon works close to the breast, allowing for very precise placement of the implant.
Breast Surgery
In addition to breast augmentation, there are three other types of breast surgeries.
Reduction mammoplasty, or breast reduction, is a procedure that removes extra tissue and repositions the nipple and breast crease to reduce the size of large breasts.
Mastopexy, or breast lift, is a procedure to correct sagging breasts. Surgeons remove and rejoin skin tissue to lift the breasts back into position. The tighter skin creates more support for the weight of the breast. This surgery can be done in conjunction with an augmentation or reduction.
When breasts have been removed or damaged, plastic surgeons use breast reconstruction to rebuild them. By getting tissue from other parts of the body and stretching abdominal tissue, new breasts can be built over implants. There are many techniques involved in restoring a natural look: In some mastectomy cases, the nipple can be removed from the old breast and attached to the new breast; another method involves a special kind of tattooing that creates the look of a nipple on a reconstructed breast.
Inframammary Fold Incision
The inframammary fold incision is another very common incision used for breast augmentation. Like the nipple incision, this incision allows for all three placement types and both insertion and removal of the implant.
The incision is made in the crease under the breast, allowing for discreet scarring. Once the incision is made, the implant is inserted and worked vertically into place. This bypasses the milk ducts, so the protective sleeve is not necessary.
When increasing breast size considerably, the surgeon often has to create a new crease in order to center the nipple on the new, larger breast and to accommodate the large implant. This presents one of the only disadvantages of this type of incision: A certain amount of guesswork goes into crease placement. However, misplacing the crease is a very rare complication and can usually be dealt with in a revision surgery.
Top Jobs
According to the American Society for Aesthetic Plastic Surgery, the top five surgical cosmetic procedures in 2003 were:
Liposuction - 384,626
Breast augmentation - 280,401
Eyelid surgery - 267,627
Rhinoplasty -172,420
Breast reduction - 147,143
Transaxillary Incision
Patients who want no breast scarring at all often opt for the more difficult transaxillary incision. This incision is made in the armpit and leaves a tiny scar that is virtually impossible to see.
The transaxillary procedure can be preformed with or without the help of an endoscope (a tube with a small surgical camera on the end). The cut is made in the fold of the armpit and a channel is cut to the breast. The implant is inserted into the channel and worked into place.
Transaxillary incision presents a greater challenge for surgeons because working that far away from the breast makes placement more difficult.
Like nipple and crease incisions, the armpit incision can be used for implant placement anywhere in the breast. The biggest draw back of the transaxillary incision is that if a complication occurs that requires revision or removal, then chances are the surgeon will have to make a nipple or crease incision to work on the implant. It is very rare that surgeons can reuse the transaxillary incision -- it's very difficult to work on an implant that far away from the breast
TUBA Incision
The TUBA (trans-umbilical breast augmentation) incision, or the bellybutton incision, is much less common than the other three. This incision is made in the rim of the bellybutton. Then, using an endoscope, a tunnel is cut through the subcutaneous fat just below the skin all the way to behind the breast. As in all techniques, a pocket is then cut for the implant. The implant is rolled up and pushed through the tunnel into place.
In this technique, the implant is filled before the incision is closed using a fill tube that is snaked through that tunnel. The surgeon uses the endoscope to make sure everything is in place and then closes the incision.
While this may seem extreme, this is actually one of the least invasive techniques. The skin on the abdomen has greater elasticity than other types of skin and can take the tunneling. Very rarely, this procedure leaves "V" tracks on the stomach. Overall, the scarring and recovery time is far less with a TUBA incision than with the other three.
There are limitations with the TUBA incision:
The procedure requires inflatable implants.
TUBA can only be used for sub-pectoral or sub-muscular placement.
In the event of complication or revision, the TUBA incision (like the armpit incision) cannot be reused -- the surgeon will have to make a nipple or crease incision to work on the implant.
Few plastic surgeons are willing or able to perform it -- this procedure makes for the greatest room for error when placing the implant due to the distance from the breast
Risks
As with all surgeries, there are risk associated with breast augmentation. First and foremost, there is the risk of infection. Unusually high fevers are generally an indication of infection after surgery, and patients should watch for this after any invasive medical procedure.
Let's go over some of the risks specific to implant surgery.
Bottoming Out
This is the effect created when the implant sits too low and the nipple rides to high. This creates an unnatural look that is the result of cutting too large a pocket for the implant. It can also be caused by the weight of the implant in thin-skinned women. This is correctable with additional surgery.
Capsule Contracture
Capsular contracture is not a risk or complication in the traditional sense: It is definitely going to happen to a certain degree. It's the amount of contracture that is the issue. Capsule contracture causes the implant to be squeezed by the fibrous scar tissue that forms around it. The result can be a painful hardening of the breasts. This is the most common complication of breast-augmentation surgery. It is dealt with in a revision surgery where the scar tissue is scraped out to make more room for the implant. It can sometimes take several of these surgeries to correct the problem.
Hematoma
This is a common surgical risk that is caused by blood pooling under the skin. It can create discolored, possibly painful lumps. This can be corrected with surgery or drainage.
Interference with Mammography
The saline or silicone in breast implants can obscure X-ray results and hide potentially cancerous growths. Submuscular is the best placement to reduce this risk. It is important that the radiologist knows the patient has implants when performing a mammography, as there are techniques that can be used to help work around them.
Necrosis
Necrosis or "tissue death" is a rare and serious complication. Dead tissue can form around the implant and prevent healing. This has to be dealt with by surgery or complete removal of the implant. Necrosis usually leaves large, permanent scars.
Rupture
While women with breast implants can participate in a variety of activities without fear, they must be mindful that their implants are not indestructible. Most breast implants come with a lifetime manufacturer's warranty that covers operational failure. But many things that cause implants to rupture are not covered by warranty, and some things (like certain surgeries and over- or under-filling) will actually void the warranty.
Seroma
Seroma is a collection of fluid around the implant. This minor problem is handled by draining the fluid with a needle.
Symmastia
Symmastia is one of the rarest risks -- it is the result of a surgical mistake that causes the implants to lift off the sternum. The result is one large breast across the front of the body, with no cleavage. This complication is hard to repair.
Traction Rippling
This occurs when a textured implant settles into place after the swelling has gone down. As the implant drops, it pulls on the scar tissue, which pulls on the skin. The result is a rippling in the breast. Only the use of smooth implants eliminates this risk.
Breast augmentation is one of the most common types of plastic surgery today. As with all surgeries (especially elective ones), it is important to understand the risks involved. For the most current and detailed information on all of the risks associated with breast augmentation, consult a qualified physician.
How Hair Coloring Works
For a long time, hair coloring has been serious business! For example, would-be heroes of ancient Greece used harsh soaps and bleaches to lighten and redden their hair to the color that was identified with honor and courage. First-century Romans preferred dark hair, which was made so by a dye concocted from boiled walnuts and leeks.
Today, hair color remains hot, with a booming 75 percent of American women reportedly coloring their hair. (In 1950, only about 7 percent of American women colored their hair. And when they did, they did it to cover gray with their natural color and usually didn't want anyone to know they'd done it!) Women have also decided that blondes don't necessarily "have more fun!" Red is currently the most requested color at beauty salons. And women aren't alone...
Men increasingly cover gray or, following the female lead, completely change their look. Men's home hair-color sales reached $113.5 million last year, a 50 percent increase in just five years. The selection of coloring products and techniques is mind-boggling. Home coloring is less expensive -- ranging from about $4 to $10 per coloring (unless you have so much hair you need two packages!) -- than a trip to the salon, which, depending upon your hair length, color and the method used, can cost $50 and up.
In this edition of How Stuff Works, we'll tackle the most important questions about hair coloring:
When should I go to a professional and when is a home job all right?
What formula and color should I choose and how will my hair react? And...
What if I really mess things up and end up looking like the neighbor's calico cat?
Don't worry -- we'll fill you in on how to prevent blunders as well as how to deal with them when they occur!
What Exactly Is Hair?
Typical mammalian hair consists of the shaft, protruding above the skin, and the root, which is sunk in a follicle, or pit, beneath the skin surface. Except for a few growing cells at the base of the root, the hair is dead tissue and is composed of keratin and related proteins. The hair follicle is a tubelike pocket of the epidermis, (see How Skin Works) that encloses a small section of the dermis at its base. Human hair is formed by rapid divisions of cells at the base of the follicle. As the cells are pushed upward from the follicle's base, they harden and undergo pigmentation.
The hair on our scalps and in our eyebrows and eyelashes are different from other bodily hairs. The hair on our heads grows a healthy .5 inch per month, and long scalp hairs have an average life of 3 to 5 years. Most of us have between 100,000 and 150,000 hairs on our heads!
There are two kinds of melanin found in the hair: eumelanin (the most common and responsible for hair shades from brown to black) and phaeomelanin (responsible for yellowish-blond, ginger and red colors). Absence of pigment produces white/gray hair. Before any permanent color can be deposited into the hair shaft, the cuticle, or outer layer, must be opened. The insoluble formula then reacts with the cortex to deposit or remove the color.
What Are the Ingredients in Hair Color?
Until the early 1900s, hair coloring was made from a wide range of herbal and natural dyes. Flying in the face of other chemists who found the development of hair coloring trivial and unworthy of their time, French chemist Eugene Schuller created the first safe commercial hair coloring in 1909. His invention was based on a new chemical, paraphenylenediamine, and provided the foundation of his company, the French Harmless Hair Dye Company. A year later, the name was changed to one that is more familiar today -- L'Oreal. L'Oreal, one of the hair product giants, has grown steadily over the years; the company credits advanced and applied research of new product development and expansion into markets around the world with its global success.
The two main chemical ingredients involved in any coloring process that lasts longer than 12 shampoos are:
Hydrogen peroxide (also known as the developer or oxidizing agent) -- This ingredient, in varying forms and strengths, helps initiate the color-forming process and creates longer-lasting color. The larger the volume of the developer, the greater the amount of sulfur is removed from the hair. Loss of sulfur causes hair to harden and lose weight. This is why, for the majority of hair coloring, the developer is maintained at 30% volume or less.
Ammonia -- This alkaline allows for lightening by acting as a catalyst when the permanent hair color comes together with the peroxide. Like all alkalines, ammonia tends to separate the cuticle and allow the hair color to penetrate the cortex of the hair.
In addition, various types of alcohols, which can also dry the hair, are present in most hair color. (Check out this official ingredient list for a hair color formula.)
How Do Hair Coloring Products Work?
The good news is that most hair color products today have nicer smells than the tell-tale rotten-egg odor that once accompanied permanents or hair coloring. And most color can be applied easily: some to wet hair, others to dry hair, worked into a shampoo-like lather, left to process (some formulas call for covering with a plastic cap during processing; others do not) and then rinsed and conditioned.
The down side is still that chemicals in hair coloring can be harsh and harmful to your hair if you don't know what you're doing or if you color or perm too often. How peroxide and ammonia react with your hair is directly related to the level and kind of product you're using. Here are basic descriptions of the three major hair coloring product levels used by Clairol, L'oreal and others:
Level 1, semi-permanent color -- This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair's cuticle, or outer layer, and go into your hair's cortex. They don't interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment. This level generally lasts for 6 to 12 shampoos, covers up to 50 percent gray, enhances your natural color and leaves no roots. This hair coloring won't lighten your hair color because it contains no ammonia or peroxide.
Level 2, demi-permanent color -- This product level lasts longer, through 24 to 26 shampoos. In this process, pre-color molecules penetrate the cuticle and enter the cortex where they then partner to create medium-sized color molecules. Their larger size means they take longer to wash out. These products do not contain ammonia so the natural pigment can't be lightened. However, it contains a small amount of peroxide, which allows for a subtle, but noticeable, color enhancement. It also blends and covers gray. (Both semi- and demi-permanent colors can become permanent on permed or already-colored hair!)
Level 3, permanent color -- This is what you need for a more significant color change (to go from black to blond, you'll still need to go with a process called double process blonding and it'd be wise to get this it done professionally). In this level, both ammonia and peroxide are used. Tiny molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. Your hair actually has to grow out over time. This product acts to lighten the hair's natural pigment to form a new base and then to add a new permanent color. The end result is a combination of your natural hair pigment and the new shade you chose. That means the color may appear different on you than on someone else using the same color. (That's why the "strand test" is so important -- more about that later.) Regular touch-ups of 4 to 6 weeks are generally needed to eliminate roots -- hair with your natural color growing at half an inch per month from your scalp.
There are also hair coloring products known as "special effect" hair colors. These are the kits you buy to add highlights or streaks to your hair. They are available in varying strengths. Some are for adding highlights to natural, uncolored hair while others are made for adding highlights to already-colored hair. Double process hair color, or bleaching and toning to achieve drastic color changes, falls into this category. Most professionals recommend you don't try this one at home unless you're really adventurous and love to experiment! Newer products on the market include color-enhancing shampoos and mousses and shampoos that keep your color vivid longer.
Now that we've reviewed the different product levels used in hair coloring, let's look at what actually happens to your hair. For example, if you're blonde and are going darker -- to brown -- permanent hair color uses the interaction between the ammonia and the peroxide to create a new color base in your hair shafts. If you go in the opposite direction -- from black or brown to blonde -- the hair goes through an additional step. First, bleach is used to strip the color from the hair. Then the ammonia-peroxide reaction creates the new color and deposits it in the hair shaft. If you use a semi-permanent color, the hair is coated with color, rather than deposited into the hair shaft.
How Do I Choose the Right Hair Color -- and the Right Product -- for Me?
Choosing a new hair color isn't as simple as finding a color you like on a box in the drugstore. You need to make this choice based on an analysis of your natural hair color, eye color and skin tone. First, let's review the basic "laws" of color. Color, as we see it, is actually the reflection of light off of the colored pigments in the hair shaft. It's sort of like the color prisms you saw in elementary school: it fractured light into distinctive colors you could see. This is what happens with hair color except that you're adding or subtracting colors to change from one color to another or to change the undertones.
A shade of color is made up of different combinations of reflections off the pigments. That's why hair color -- both natural and dyed -- looks different under fluorescent lights and in natural sunlight. Color levels are the degrees of lightness or darkness of a color seen by the eye. Hair color is assigned a level number from 1 to 10, with 10 being the lightest and 1 being black. Black reflects very little light and the lightest shades of blonde reflect the greatest amount of light. A colorist would say that a level 10 blonde is two steps lighter than a level 8 blonde.
Look at a color wheel or chart: Suppose you want to lighten your hair color. When hair is lightened, it produces warm, or yellow-red, undertones. Remember from school that mixing yellow and red produces orange -- not generally the desired hair color! Refer to the wheel to cancel out some of the orange tone but leave enough to keep the warm tones. The best hair colors for you if you have warm skin undertones (ivory, peachy, golden brown, creamy beige, cafe au lait, tawny, coppery, deep golden brown) and blue, blue-green hazel, green, topaz, amber or coffeebean colored eyes, are golden with red highlights, golden brown, honey brown, chestnut, copper and mahogany. Cool tones are blue-red. If your skin has rosy pink, rosy beige, dark olive, dark brown or ebony tones and your eyes are light blue, gray-blue, deep blue, deep green, brown or black, your best hair color options are plum and burgundy highlights, ash and platinum blonde, brown, dark brown, black, slate, salt and pepper and pure white.
How Do I Choose the Right Hair Color -- and the Right Product -- for Me?
Choosing a new hair color isn't as simple as finding a color you like on a box in the drugstore. You need to make this choice based on an analysis of your natural hair color, eye color and skin tone. First, let's review the basic "laws" of color. Color, as we see it, is actually the reflection of light off of the colored pigments in the hair shaft. It's sort of like the color prisms you saw in elementary school: it fractured light into distinctive colors you could see. This is what happens with hair color except that you're adding or subtracting colors to change from one color to another or to change the undertones.
A shade of color is made up of different combinations of reflections off the pigments. That's why hair color -- both natural and dyed -- looks different under fluorescent lights and in natural sunlight. Color levels are the degrees of lightness or darkness of a color seen by the eye. Hair color is assigned a level number from 1 to 10, with 10 being the lightest and 1 being black. Black reflects very little light and the lightest shades of blonde reflect the greatest amount of light. A colorist would say that a level 10 blonde is two steps lighter than a level 8 blonde.
say you also can't miss if you return your hair to its color when you were 12 years old! (To have some fun, try MakeoverStudio.com, which gives you some idea of how you'd look as a redhead -- or a blonde!)
Your choice of hair coloring product depends on what you're trying to accomplish and how long you want your color to last. Most women start with a lower commitment level and move up to a higher level over time. If you're seeing more gray or your hair coloring isn't covering gray as well as it did, you might need to move to a higher-level product. Level 3 is the only kind of product that can completely and permanently cover any amount of gray.
The all-important strand test (always explained in home coloring packages) will ensure that you've chosen the right color -- and product -- and will give you a chance to change your mind. It works like this:
Mix one teaspoon of color and one teaspoon of developer (peroxide) in a glass bowl.
Apply the mixture to the roots or ends to determine the outcome. You can protect the test strand from the other hair by wrapping a piece of tin foil around the strand and securing it with a clip.
Time the process according to package directions, then rinse and dry the strand.
Look at it in different types of light to see if you like it.
Look at a color wheel or chart: Suppose you want to lighten your hair color. When hair is lightened, it produces warm, or yellow-red, undertones. Remember from school that mixing yellow and red produces orange -- not generally the desired hair color! Refer to the wheel to cancel out some of the orange tone but leave enough to keep the warm tones. The best hair colors for you if you have warm skin undertones (ivory, peachy, golden brown, creamy beige, cafe au lait, tawny, coppery, deep golden brown) and blue, blue-green hazel, green, topaz, amber or coffeebean colored eyes, are golden with red highlights, golden brown, honey brown, chestnut, copper and mahogany. Cool tones are blue-red. If your skin has rosy pink, rosy beige, dark olive, dark brown or ebony tones and your eyes are light blue, gray-blue, deep blue, deep green, brown or black, your best hair color options are plum and burgundy highlights, ash and platinum blonde, brown, dark brown, black, slate, salt and pepper and pure white.
Is there a way to make my sunglasses scratch-resistant?
Reflective sunglasses often have a mirrored look. The lenses in these sunglasses have a reflective coating applied in a very thin, sparse layer -- so thin that it's called a half-silvered surface. The name half-silvered comes from the fact that at the molecular level, there are reflective molecules speckled over the glass in an even film, but only half of the glass is actually covered. The half-silvered surface will reflect about half the light that strikes it, letting the other half go straight through.
Often, the mirror coating is applied as a gradient that gradually changes shades from top to bottom. This provides additional protection from light coming in from above, while allowing more light to come in from below or straight ahead. This means that if you are driving, the sun's rays are blocked but you can still see the dashboard. Sometimes, the coating is bi-gradient, shading from mirrored at the top and bottom to clear in the middle.
The key problem with reflective sunglasses is that the coating is easily scratched. While glass itself is naturally scratch resistant, the coatings applied to glass, as well as to most plastic lenses, are not. To compensate for this, manufacturers have developed a variety of ways to apply optically clear, hard films to lenses. These films are made of materials such as diamond-like carbon (DLC) and polycrystalline diamond. Through a process of ionization, a thin but extremely durable film is created on the surface of the lens. See Patent #5,268,217 for details.
This scratch-resistant coating works well in most cases. But sunglass manufacturers have not been able to successfully apply a scratch-resistant layer on top of the reflective coating used on mirrored sunglasses. Therefore, the scratch-resistant coating is applied first, to protect the lenses, and the reflective coating is applied over it.
How Solar Cells Work
You've probably seen calculators that have solar cells -- calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels -- on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot if you know where to look. There are solar cell arrays on satellites, where they are used to power the electrical systems.
You have probably also been hearing about the "solar revolution" for the last 20 years -- the idea that one day we will all use free electricity from the sun. This is a seductive promise: On a bright, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that energy we could easily power our homes and offices for free.
In this article, we will examine solar cells to learn how they convert the sun's energy directly into electricity. In the process, you will learn why we are getting closer to using the sun's energy on a daily basis, and why we still have more research to do before the process becomes cost effective.
Photovoltaic Cells: Converting Photons to Electrons
The solar cells that you see on calculators and satellites are photovoltaic cells or modules (modules are simply a group of cells electrically connected and packaged in one frame). Photovoltaics, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. Once used almost exclusively in space, photovoltaics are used more and more in less exotic ways. They could even power your house. How do these devices work?
Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally. For example, the current can power a calculator. This current, together with the cell's voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.
That's the basic process, but there's really much more to it. Let's take a deeper look into one example of a PV cell: the single-crystal silicon cell.
How Silicon Makes a Solar Cell
Silicon has some special chemical properties, especially in its crystalline form. An atom of silicon has 14 electrons, arranged in three different shells. The first two shells, those closest to the center, are completely full. The outer shell, however, is only half full, having only four electrons. A silicon atom will always look for ways to fill up its last shell (which would like to have eight electrons). To do this, it will share electrons with four of its neighbor silicon atoms. It's like every atom holds hands with its neighbors, except that in this case, each atom has four hands joined to four neighbors. That's what forms the crystalline structure, and that structure turns out to be important to this type of PV cell.
We've now described pure, crystalline silicon. Pure silicon is a poor conductor of electricity because none of its electrons are free to move about, as electrons are in good conductors such as copper. Instead, the electrons are all locked in the crystalline structure. The silicon in a solar cell is modified slightly so that it will work as a solar cell.
A solar cell has silicon with impurities -- other atoms mixed in with the silicon atoms, changing the way things work a bit. We usually think of impurities as something undesirable, but in our case, our cell wouldn't work without them. These impurities are actually put there on purpose. Consider silicon with an atom of phosphorous here and there, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer shell, not four. It still bonds with its silicon neighbor atoms, but in a sense, the phosphorous has one electron that doesn't have anyone to hold hands with. It doesn't form part of a bond, but there is a positive proton in the phosphorous nucleus holding it in place.
When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind in each case. These electrons then wander randomly around the crystalline lattice looking for another hole to fall into. These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful. Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons because they aren't tied up in a bond -- their neighbors aren't holding them back. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon. The process of adding impurities on purpose is called doping, and when doped with phosphorous, the resulting silicon is called N-type ("n" for negative) because of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure silicon is.
Actually, only part of our solar cell is N-type. The other part is doped with boron, which has only three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free electrons, P-type silicon ("p" for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do.
The interesting part starts when you put N-type silicon together with P-type silicon. Remember that every PV cell has at least one electric field. Without an electric field, the cell wouldn't work, and this field forms when the N-type and P-type silicon are in contact. Suddenly, the free electrons in the N side, which have been looking all over for holes to fall into, see all the free holes on the P side, and there's a mad rush to fill them in.
Anatomy of a Solar Cell
Before now, our silicon was all electrically neutral. Our extra electrons were balanced out by the extra protons in the phosphorous. Our missing electrons (holes) were balanced out by the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted. Do all the free electrons fill all the free holes? No. If they did, then the whole arrangement wouldn't be very useful. Right at the junction, however, they do mix and form a barrier, making it harder and harder for electrons on the N side to cross to the P side. Eventually, equilibrium is reached, and we have an electric field separating the two sides.
This electric field acts as a diode, allowing (and even pushing) electrons to flow from the P side to the N side, but not the other way around. It's like a hill -- electrons can easily go down the hill (to the N side), but can't climb it (to the P side).
So we've got an electric field acting as a diode in which electrons can only move in one direction.
When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs.
Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, or if free electron and free hole happen to wander into its range of influence, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two.
There are a few more steps left before we can really use our cell. Silicon happens to be a very shiny material, which means that it is very reflective. Photons that are reflected can't be used by the cell. For that reason, an antireflective coating is applied to the top of the cell to reduce reflection losses to less than 5 percent.
The final step is the glass cover plate that protects the cell from the elements. PV modules are made by connecting several cells (usually 36) in series and parallel to achieve useful levels of voltage and current, and putting them in a sturdy frame complete with a glass cover and positive and negative terminals on the back.
How much sunlight energy does our PV cell absorb? Unfortunately, the most that our simple cell could absorb is around 25 percent, and more likely is 15 percent or less. Why so little?
Besides Single-crystal Silicon...Single-crystal silicon isn't the only material used in PV cells. Polycrystalline silicon is also used in an attempt to cut manufacturing costs, although resulting cells aren't as efficient as single crystal silicon. Amorphous silicon, which has no crystalline structure, is also used, again in an attempt to reduce production costs. Other materials used include gallium arsenide, copper indium diselenide and cadmium telluride. Since different materials have different band gaps, they seem to be "tuned" to different wavelengths, or photons of different energies. One way efficiency has been improved is to use two or more layers of different materials with different band gaps. The higher band gap material is on the surface, absorbing high-energy photons while allowing lower-energy photons to be absorbed by the lower band gap material beneath. This technique can result in much higher efficiencies. Such cells, called multi-junction cells, can have more than one electric field.
Energy Loss in a Solar Cell
Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic -- it is made up of a range of different wavelengths, and therefore energy levels. (See How Special Relativity Works for a good discussion of the electromagnetic spectrum.)
Light can be separated into different wavelengths, and we can see them in the form of a rainbow. Since the light that hits our cell has photons of a wide range of energies, it turns out that some of them won't have enough energy to form an electron-hole pair. They'll simply pass through the cell as if it were transparent. Still other photons have too much energy. Only a certain amount of energy, measured in electron volts (eV) and defined by our cell material (about 1.1 eV for crystalline silicon), is required to knock an electron loose. We call this the band gap energy of a material. If a photon has more energy than the required amount, then the extra energy is lost (unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant). These two effects alone account for the loss of around 70 percent of the radiation energy incident on our cell.
Why can't we choose a material with a really low band gap, so we can use more of the photons? Unfortunately, our band gap also determines the strength (voltage) of our electric field, and if it's too low, then what we make up in extra current (by absorbing more photons), we lose by having a small voltage. Remember that power is voltage times current. The optimal band gap, balancing these two effects, is around 1.4 eV for a cell made from a single material.
We have other losses as well. Our electrons have to flow from one side of the cell to the other through an external circuit. We can cover the bottom with a metal, allowing for good conduction, but if we completely cover the top, then photons can't get through the opaque conductor and we lose all of our current (in some cells, transparent conductors are used on the top surface, but not in all). If we put our contacts only at the sides of our cell, then the electrons have to travel an extremely long distance (for an electron) to reach the contacts. Remember, silicon is a semiconductor -- it's not nearly as good as a metal for transporting current. Its internal resistance (called series resistance) is fairly high, and high resistance means high losses. To minimize these losses, our cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can't be too small or else its own resistance will be too high.
Now that we know how a solar cell operates, let's see what it takes to power a house with the technology.
Solar-powering a House
What would you have to do to power your house with solar energy? Although it's not as simple as just slapping some modules on your roof, it's not extremely difficult to do, either.
First of all, not every roof has the correct orientation or angle of inclination to take advantage of the sun's energy. Non-tracking PV systems in the Northern Hemisphere should point toward true south (this is the orientation). They should be inclined at an angle equal to the area's latitude to absorb the maximum amount of energy year-round. A different orientation and/or inclination could be used if you want to maximize energy production for the morning or afternoon, and/or the summer or winter. Of course, the modules should never be shaded by nearby trees or buildings, no matter the time of day or the time of year. In a PV module, even if just one of its 36 cells is shaded, power production will be reduced by more than half.
If you have a house with an unshaded, south-facing roof, you need to decide what size system you need. This is complicated by the facts that your electricity production depends on the weather, which is never completely predictable, and that your electricity demand will also vary. These hurdles are fairly easy to clear. Meteorological data gives average monthly sunlight levels for different geographical areas. This takes into account rainfall and cloudy days, as well as altitude, humidity, and other more subtle factors. You should design for the worst month, so that you'll have enough electricity all year. With that data, and knowing your average household demand (your utility bill conveniently lets you know how much energy you use every month),there are simple methods you can use to determine just how many PV modules you'll need. You'll also need to decide on a system voltage, which you can control by deciding how many modules to wire in series.
You may have already guessed a couple of problems that we'll have to solve. First, what do we do when the sun isn't shining?
Solving Solar-power Issues
Certainly, no one would accept only having electricity during the day, and then only on clear days, if they have a choice. We need energy storage -- batteries. Unfortunately, batteries add a lot of cost and maintenance to the PV system. Currently, however, it's a necessity if you want to be completely independent. One way around the problem is to connect your house to the utility grid, buying power when you need it and selling to them when you produce more than you need. This way, the utility acts as a practically infinite storage system. The utility has to agree, of course, and in most cases will buy power from you at a much lower price than their own selling price. You will also need special equipment to make sure that the power you sell to your utility is synchronous with theirs -- that it shares the same sinusoidal waveform and frequency. Safety is an issue as well. The utility has to make sure that if there's a power outage in your neighborhood, your PV system won't try to feed electricity into lines that a lineman may think is dead. This is called islanding.
If you decide to use batteries, keep in mind that they will have to be maintained, and then replaced after a certain number of years. The PV modules should last 20 years or more, but batteries just don't have that kind of useful life. Batteries in PV systems can also be very dangerous because of the energy they store and the acidic electrolytes they contain, so you'll need a well-ventilated, non-metallic enclosure for them.
Although several different kinds of batteries are commonly used, the one characteristic they should all have in common is that they are deep-cycle batteries. Unlike your car battery, which is a shallow-cycle battery, deep-cycle batteries can discharge more of their stored energy while still maintaining long life. Car batteries discharge a large current for a very short time -- to start your car -- and are then immediately recharged as you drive. PV batteries generally have to discharge a smaller current for a longer period (such as all night), while being charged during the day.
The most commonly used deep-cycle batteries are lead-acid batteries (both sealed and vented) and nickel-cadmium batteries. Nickel-cadmium batteries are more expensive, but last longer and can be discharged more completely without harm. Even deep-cycle lead-acid batteries can't be discharged 100 percent without seriously shortening battery life, and generally, PV systems are designed to discharge lead-acid batteries no more than 40 percent or 50 percent.
Also, the use of batteries requires the installation of another component called a charge controller. Batteries last a lot longer if care is taken so that they aren't overcharged or drained too much. That's what a charge controller does. Once the batteries are fully charged, the charge controller doesn't let current from the PV modules continue to flow into them. Similarly, once the batteries have been drained to a certain predetermined level, controlled by measuring battery voltage, many charge controllers will not allow more current to be drained from the batteries until they have been recharged. The use of a charge controller is essential for long battery life.
The other problem besides energy storage is that the electricity generated by your PV modules, and extracted from your batteries if you choose to use them, is not in the form that's used by the electrical appliances in your house. The electricity generated by a solar system is direct current, while the electricity supplied by your utility (and the kind that every appliance in your house uses) is alternating current. You will need an inverter, a device that converts DC to AC. Most large inverters will also allow you to automatically control how your system works. Some PV modules, called AC modules, actually have an inverter already built into each module, eliminating the need for a large, central inverter, and simplifying wiring issues.
Throw in the mounting hardware, wiring, junction boxes, grounding equipment, overcurrent protection, DC and AC disconnects and other accessories and you have yourself a system. Electrical codes must be followed (there's a section in the National Electrical Code just for PV), and it's highly recommended that the installation be done by a licensed electrician who has experience with PV systems. Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years or more.
If photovoltaics are such a wonderful source of free energy, then why doesn't the whole world run on solar power?
Throw in the mounting hardware, wiring, junction boxes, grounding equipment, overcurrent protection, DC and AC disconnects and other accessories and you have yourself a system. Electrical codes must be followed (there's a section in the National Electrical Code just for PV), and it's highly recommended that the installation be done by a licensed electrician who has experience with PV systems. Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years or more.
If photovoltaics are such a wonderful source of free energy, then why doesn't the whole world run on solar power?
Solar-power Costs
Some people have a flawed concept of solar energy. While it's true that sunlight is free, the electricity generated by PV systems is not. As you can see from our discussion of a household PV system, quite a bit of hardware is needed. Currently, an installed PV system will cost somewhere around $9 per peak Watt. To give you an idea of how much a house system would cost, let's consider the Solar House -- a model residential home in Raleigh, North Carolina, with a PV system set up by the North Carolina Solar Center to demonstrate the technology. It's a fairly small home, and it is estimated that its 3.6-kW PV system covers about half of the total electricity needs (this system doesn't use batteries -- it's connected to the grid). Even so, at $9 per Watt, this installed system would cost you around $32,000.
That's why PV is usually used in remote areas, far from a conventional source of electricity. Right now, it simply can't compete with the utilities. Costs are coming down as research is being done, however. Researchers are confident that PV will one day be cost effective in urban areas as well as remote ones. Part of the problem is that manufacturing needs to be done on a large scale to reduce costs as much as possible. That kind of demand for PV, however, won't exist until prices fall to competitive levels. It's a Catch-22 situation. Even so, demand and module efficiencies are constantly rising, prices are falling, and the world is becoming increasingly aware of environmental concerns associated with conventional power sources, making photovoltaics a technology with a bright future.
You have probably also been hearing about the "solar revolution" for the last 20 years -- the idea that one day we will all use free electricity from the sun. This is a seductive promise: On a bright, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that energy we could easily power our homes and offices for free.
In this article, we will examine solar cells to learn how they convert the sun's energy directly into electricity. In the process, you will learn why we are getting closer to using the sun's energy on a daily basis, and why we still have more research to do before the process becomes cost effective.
Photovoltaic Cells: Converting Photons to Electrons
The solar cells that you see on calculators and satellites are photovoltaic cells or modules (modules are simply a group of cells electrically connected and packaged in one frame). Photovoltaics, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. Once used almost exclusively in space, photovoltaics are used more and more in less exotic ways. They could even power your house. How do these devices work?
Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally. For example, the current can power a calculator. This current, together with the cell's voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.
That's the basic process, but there's really much more to it. Let's take a deeper look into one example of a PV cell: the single-crystal silicon cell.
How Silicon Makes a Solar Cell
Silicon has some special chemical properties, especially in its crystalline form. An atom of silicon has 14 electrons, arranged in three different shells. The first two shells, those closest to the center, are completely full. The outer shell, however, is only half full, having only four electrons. A silicon atom will always look for ways to fill up its last shell (which would like to have eight electrons). To do this, it will share electrons with four of its neighbor silicon atoms. It's like every atom holds hands with its neighbors, except that in this case, each atom has four hands joined to four neighbors. That's what forms the crystalline structure, and that structure turns out to be important to this type of PV cell.
We've now described pure, crystalline silicon. Pure silicon is a poor conductor of electricity because none of its electrons are free to move about, as electrons are in good conductors such as copper. Instead, the electrons are all locked in the crystalline structure. The silicon in a solar cell is modified slightly so that it will work as a solar cell.
A solar cell has silicon with impurities -- other atoms mixed in with the silicon atoms, changing the way things work a bit. We usually think of impurities as something undesirable, but in our case, our cell wouldn't work without them. These impurities are actually put there on purpose. Consider silicon with an atom of phosphorous here and there, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer shell, not four. It still bonds with its silicon neighbor atoms, but in a sense, the phosphorous has one electron that doesn't have anyone to hold hands with. It doesn't form part of a bond, but there is a positive proton in the phosphorous nucleus holding it in place.
When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind in each case. These electrons then wander randomly around the crystalline lattice looking for another hole to fall into. These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful. Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons because they aren't tied up in a bond -- their neighbors aren't holding them back. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon. The process of adding impurities on purpose is called doping, and when doped with phosphorous, the resulting silicon is called N-type ("n" for negative) because of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure silicon is.
Actually, only part of our solar cell is N-type. The other part is doped with boron, which has only three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free electrons, P-type silicon ("p" for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do.
The interesting part starts when you put N-type silicon together with P-type silicon. Remember that every PV cell has at least one electric field. Without an electric field, the cell wouldn't work, and this field forms when the N-type and P-type silicon are in contact. Suddenly, the free electrons in the N side, which have been looking all over for holes to fall into, see all the free holes on the P side, and there's a mad rush to fill them in.
Anatomy of a Solar Cell
Before now, our silicon was all electrically neutral. Our extra electrons were balanced out by the extra protons in the phosphorous. Our missing electrons (holes) were balanced out by the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted. Do all the free electrons fill all the free holes? No. If they did, then the whole arrangement wouldn't be very useful. Right at the junction, however, they do mix and form a barrier, making it harder and harder for electrons on the N side to cross to the P side. Eventually, equilibrium is reached, and we have an electric field separating the two sides.
This electric field acts as a diode, allowing (and even pushing) electrons to flow from the P side to the N side, but not the other way around. It's like a hill -- electrons can easily go down the hill (to the N side), but can't climb it (to the P side).
So we've got an electric field acting as a diode in which electrons can only move in one direction.
When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs.
Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, or if free electron and free hole happen to wander into its range of influence, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two.
There are a few more steps left before we can really use our cell. Silicon happens to be a very shiny material, which means that it is very reflective. Photons that are reflected can't be used by the cell. For that reason, an antireflective coating is applied to the top of the cell to reduce reflection losses to less than 5 percent.
The final step is the glass cover plate that protects the cell from the elements. PV modules are made by connecting several cells (usually 36) in series and parallel to achieve useful levels of voltage and current, and putting them in a sturdy frame complete with a glass cover and positive and negative terminals on the back.
How much sunlight energy does our PV cell absorb? Unfortunately, the most that our simple cell could absorb is around 25 percent, and more likely is 15 percent or less. Why so little?
Besides Single-crystal Silicon...Single-crystal silicon isn't the only material used in PV cells. Polycrystalline silicon is also used in an attempt to cut manufacturing costs, although resulting cells aren't as efficient as single crystal silicon. Amorphous silicon, which has no crystalline structure, is also used, again in an attempt to reduce production costs. Other materials used include gallium arsenide, copper indium diselenide and cadmium telluride. Since different materials have different band gaps, they seem to be "tuned" to different wavelengths, or photons of different energies. One way efficiency has been improved is to use two or more layers of different materials with different band gaps. The higher band gap material is on the surface, absorbing high-energy photons while allowing lower-energy photons to be absorbed by the lower band gap material beneath. This technique can result in much higher efficiencies. Such cells, called multi-junction cells, can have more than one electric field.
Energy Loss in a Solar Cell
Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic -- it is made up of a range of different wavelengths, and therefore energy levels. (See How Special Relativity Works for a good discussion of the electromagnetic spectrum.)
Light can be separated into different wavelengths, and we can see them in the form of a rainbow. Since the light that hits our cell has photons of a wide range of energies, it turns out that some of them won't have enough energy to form an electron-hole pair. They'll simply pass through the cell as if it were transparent. Still other photons have too much energy. Only a certain amount of energy, measured in electron volts (eV) and defined by our cell material (about 1.1 eV for crystalline silicon), is required to knock an electron loose. We call this the band gap energy of a material. If a photon has more energy than the required amount, then the extra energy is lost (unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant). These two effects alone account for the loss of around 70 percent of the radiation energy incident on our cell.
Why can't we choose a material with a really low band gap, so we can use more of the photons? Unfortunately, our band gap also determines the strength (voltage) of our electric field, and if it's too low, then what we make up in extra current (by absorbing more photons), we lose by having a small voltage. Remember that power is voltage times current. The optimal band gap, balancing these two effects, is around 1.4 eV for a cell made from a single material.
We have other losses as well. Our electrons have to flow from one side of the cell to the other through an external circuit. We can cover the bottom with a metal, allowing for good conduction, but if we completely cover the top, then photons can't get through the opaque conductor and we lose all of our current (in some cells, transparent conductors are used on the top surface, but not in all). If we put our contacts only at the sides of our cell, then the electrons have to travel an extremely long distance (for an electron) to reach the contacts. Remember, silicon is a semiconductor -- it's not nearly as good as a metal for transporting current. Its internal resistance (called series resistance) is fairly high, and high resistance means high losses. To minimize these losses, our cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can't be too small or else its own resistance will be too high.
Now that we know how a solar cell operates, let's see what it takes to power a house with the technology.
Solar-powering a House
What would you have to do to power your house with solar energy? Although it's not as simple as just slapping some modules on your roof, it's not extremely difficult to do, either.
First of all, not every roof has the correct orientation or angle of inclination to take advantage of the sun's energy. Non-tracking PV systems in the Northern Hemisphere should point toward true south (this is the orientation). They should be inclined at an angle equal to the area's latitude to absorb the maximum amount of energy year-round. A different orientation and/or inclination could be used if you want to maximize energy production for the morning or afternoon, and/or the summer or winter. Of course, the modules should never be shaded by nearby trees or buildings, no matter the time of day or the time of year. In a PV module, even if just one of its 36 cells is shaded, power production will be reduced by more than half.
If you have a house with an unshaded, south-facing roof, you need to decide what size system you need. This is complicated by the facts that your electricity production depends on the weather, which is never completely predictable, and that your electricity demand will also vary. These hurdles are fairly easy to clear. Meteorological data gives average monthly sunlight levels for different geographical areas. This takes into account rainfall and cloudy days, as well as altitude, humidity, and other more subtle factors. You should design for the worst month, so that you'll have enough electricity all year. With that data, and knowing your average household demand (your utility bill conveniently lets you know how much energy you use every month),there are simple methods you can use to determine just how many PV modules you'll need. You'll also need to decide on a system voltage, which you can control by deciding how many modules to wire in series.
You may have already guessed a couple of problems that we'll have to solve. First, what do we do when the sun isn't shining?
Solving Solar-power Issues
Certainly, no one would accept only having electricity during the day, and then only on clear days, if they have a choice. We need energy storage -- batteries. Unfortunately, batteries add a lot of cost and maintenance to the PV system. Currently, however, it's a necessity if you want to be completely independent. One way around the problem is to connect your house to the utility grid, buying power when you need it and selling to them when you produce more than you need. This way, the utility acts as a practically infinite storage system. The utility has to agree, of course, and in most cases will buy power from you at a much lower price than their own selling price. You will also need special equipment to make sure that the power you sell to your utility is synchronous with theirs -- that it shares the same sinusoidal waveform and frequency. Safety is an issue as well. The utility has to make sure that if there's a power outage in your neighborhood, your PV system won't try to feed electricity into lines that a lineman may think is dead. This is called islanding.
If you decide to use batteries, keep in mind that they will have to be maintained, and then replaced after a certain number of years. The PV modules should last 20 years or more, but batteries just don't have that kind of useful life. Batteries in PV systems can also be very dangerous because of the energy they store and the acidic electrolytes they contain, so you'll need a well-ventilated, non-metallic enclosure for them.
Although several different kinds of batteries are commonly used, the one characteristic they should all have in common is that they are deep-cycle batteries. Unlike your car battery, which is a shallow-cycle battery, deep-cycle batteries can discharge more of their stored energy while still maintaining long life. Car batteries discharge a large current for a very short time -- to start your car -- and are then immediately recharged as you drive. PV batteries generally have to discharge a smaller current for a longer period (such as all night), while being charged during the day.
The most commonly used deep-cycle batteries are lead-acid batteries (both sealed and vented) and nickel-cadmium batteries. Nickel-cadmium batteries are more expensive, but last longer and can be discharged more completely without harm. Even deep-cycle lead-acid batteries can't be discharged 100 percent without seriously shortening battery life, and generally, PV systems are designed to discharge lead-acid batteries no more than 40 percent or 50 percent.
Also, the use of batteries requires the installation of another component called a charge controller. Batteries last a lot longer if care is taken so that they aren't overcharged or drained too much. That's what a charge controller does. Once the batteries are fully charged, the charge controller doesn't let current from the PV modules continue to flow into them. Similarly, once the batteries have been drained to a certain predetermined level, controlled by measuring battery voltage, many charge controllers will not allow more current to be drained from the batteries until they have been recharged. The use of a charge controller is essential for long battery life.
The other problem besides energy storage is that the electricity generated by your PV modules, and extracted from your batteries if you choose to use them, is not in the form that's used by the electrical appliances in your house. The electricity generated by a solar system is direct current, while the electricity supplied by your utility (and the kind that every appliance in your house uses) is alternating current. You will need an inverter, a device that converts DC to AC. Most large inverters will also allow you to automatically control how your system works. Some PV modules, called AC modules, actually have an inverter already built into each module, eliminating the need for a large, central inverter, and simplifying wiring issues.
Throw in the mounting hardware, wiring, junction boxes, grounding equipment, overcurrent protection, DC and AC disconnects and other accessories and you have yourself a system. Electrical codes must be followed (there's a section in the National Electrical Code just for PV), and it's highly recommended that the installation be done by a licensed electrician who has experience with PV systems. Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years or more.
If photovoltaics are such a wonderful source of free energy, then why doesn't the whole world run on solar power?
Throw in the mounting hardware, wiring, junction boxes, grounding equipment, overcurrent protection, DC and AC disconnects and other accessories and you have yourself a system. Electrical codes must be followed (there's a section in the National Electrical Code just for PV), and it's highly recommended that the installation be done by a licensed electrician who has experience with PV systems. Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years or more.
If photovoltaics are such a wonderful source of free energy, then why doesn't the whole world run on solar power?
Solar-power Costs
Some people have a flawed concept of solar energy. While it's true that sunlight is free, the electricity generated by PV systems is not. As you can see from our discussion of a household PV system, quite a bit of hardware is needed. Currently, an installed PV system will cost somewhere around $9 per peak Watt. To give you an idea of how much a house system would cost, let's consider the Solar House -- a model residential home in Raleigh, North Carolina, with a PV system set up by the North Carolina Solar Center to demonstrate the technology. It's a fairly small home, and it is estimated that its 3.6-kW PV system covers about half of the total electricity needs (this system doesn't use batteries -- it's connected to the grid). Even so, at $9 per Watt, this installed system would cost you around $32,000.
That's why PV is usually used in remote areas, far from a conventional source of electricity. Right now, it simply can't compete with the utilities. Costs are coming down as research is being done, however. Researchers are confident that PV will one day be cost effective in urban areas as well as remote ones. Part of the problem is that manufacturing needs to be done on a large scale to reduce costs as much as possible. That kind of demand for PV, however, won't exist until prices fall to competitive levels. It's a Catch-22 situation. Even so, demand and module efficiencies are constantly rising, prices are falling, and the world is becoming increasingly aware of environmental concerns associated with conventional power sources, making photovoltaics a technology with a bright future.
13.3.08
How To Choose a Cool MP3 Player
An MP3 player is a very smart electronic device that can be combined with other things to help you to listen to your favorite music and songs anywhere and anytime. The best thing here is the ability of downloading the music files from you laptop or PC to your portable MP3 gadget, using an USB cable for fast connection. The other cool thing is that an MP3 player can be within other essential thing in our life like sunglasses, a wristwatch, alarm clock and much more.
MP3 player sunglasses: Enjoy the best music while protecting your eyes. The sunglasses come with a built-in digital MP3 player with all features like the ability of downloading music files in all formats like MP1, MP2, MP3, WMA, WAV, etc. You can download those files by using the USB cable that should come with it after purchasing.
To have the ability to record voice digitally, you should ensure that these MP3 sunglasses have a built-in microphone for digital voice recording. Other features of interest while buying MP3 sunglasses are the supporting of equalizer bands and the presence of lithium rechargeable battery. Some models may come with a built-in Bluetooth headset to download the music files wirelessly; this is also a great feature.
MP3 watches: In this gadget, the MP3 player will be within an ordinary wristwatch. So, you can enjoy your favorite music wherever you go as the MP3 watch will provide all the features of a regular digital MP3 player. The presence of built-in digital MP3 player within the wrist watch makes it easy to listen to music and songs, record voice digitally and record lectures (so it's good for school and college students), and of course it will be easy to download and upload files. In other words, this gadget is perfect as a gift.
MP3 alarm clock: Another great MP3 gadget that give the chance to wake up with a personal message. With this alarm clock you can download all music files like MP3, WAV and other file formats to wake up with your favorite song. You can also wake up with a message from your friend, lover, etc. When you decide to purchase one of these MP3 player alarm clocks, you should be sure that this gadget provides the essential tools to download the music files, such as the USB cable and the rechargeable memory.
Now you can choose one of these MP3 gadgets to give a cool gift tomorrow.
MP3 player sunglasses: Enjoy the best music while protecting your eyes. The sunglasses come with a built-in digital MP3 player with all features like the ability of downloading music files in all formats like MP1, MP2, MP3, WMA, WAV, etc. You can download those files by using the USB cable that should come with it after purchasing.
To have the ability to record voice digitally, you should ensure that these MP3 sunglasses have a built-in microphone for digital voice recording. Other features of interest while buying MP3 sunglasses are the supporting of equalizer bands and the presence of lithium rechargeable battery. Some models may come with a built-in Bluetooth headset to download the music files wirelessly; this is also a great feature.
MP3 watches: In this gadget, the MP3 player will be within an ordinary wristwatch. So, you can enjoy your favorite music wherever you go as the MP3 watch will provide all the features of a regular digital MP3 player. The presence of built-in digital MP3 player within the wrist watch makes it easy to listen to music and songs, record voice digitally and record lectures (so it's good for school and college students), and of course it will be easy to download and upload files. In other words, this gadget is perfect as a gift.
MP3 alarm clock: Another great MP3 gadget that give the chance to wake up with a personal message. With this alarm clock you can download all music files like MP3, WAV and other file formats to wake up with your favorite song. You can also wake up with a message from your friend, lover, etc. When you decide to purchase one of these MP3 player alarm clocks, you should be sure that this gadget provides the essential tools to download the music files, such as the USB cable and the rechargeable memory.
Now you can choose one of these MP3 gadgets to give a cool gift tomorrow.
How To Edit a Home Video
If you are a first time movie editor, you already have most of the tools to get started and probably don't even know it. Fortunately, video editing has become a lot easier and is now orientated towards everyone, so that even the non-computer savvy can learn to edit a mean video.
First, you will need to pick up a video editing software program. Forunately, you probably have one loaded on your computer and don't even know it. Windows XP comes with windows video maker program that should be already installed on your system. The program makes WMV files, which should play directly on your computer, or gives you a few other file options. Not to mention, this program is packed with features that should satisfy your video editing needs!.
Once you've opened the program, you will need to import your video. Simply hook up your digital camera, locate the video, and voila, the program does the rest for you. It even separates the video into small chunks, based on changes to the video. It is one smart program! You can import other video files, music, or photos all to use in your video. Import everything you will use, and move onto the next step.
Now that you have everything imported, your next step is creating your timeline. Simply drag and drop clips. The program will let you preview every clip to see what is on it. Once you add them to your timeline, this is like adding them to your movie. You can stretch and drag the individual chunks, and this will manage which portions you want to appear on your video. Construct your entire video this way, and you are ready to create some video editing magic.
You will notice two other portions to your video timeline. The first of which is music. If you imported a couple of songs, you can drag and drop them, and this will cause music to play along with your video, which is definitely a nice touch to any movie. The other bar allows you to drop words or pictures on the screen. Click on the side menu which says add credits, and explore all the available options. You can make crazy words do whatever you want to describe the action, or simply point out something interesting. And feel free to create credits at the end of your video.
Finally, your video is in desperate need of a little flare. By right-clicking on any of your video chunks, you can manage special effects between scenes. Fade in and out, flutter the pages, or you can do some interesting things to a scene like making it appear in black and white, or making it look like an old movie camera. Experiment with all the special effects until you create something you love.
When you are done creating your masterpiece, you can preview the whole thing by pressing play. When you are satisfied, you have to save your movie by going to the File -> Save Movie bar. You should see plenty of different options, like saving your movie to play on your computer, or saving it so that you can burn it onto a DVD. Choose which option you'd like, and watch as your movie is created on your computer.
Now you are done! Time to share your movie with the rest of the world, and see what the critics have to say about it!
First, you will need to pick up a video editing software program. Forunately, you probably have one loaded on your computer and don't even know it. Windows XP comes with windows video maker program that should be already installed on your system. The program makes WMV files, which should play directly on your computer, or gives you a few other file options. Not to mention, this program is packed with features that should satisfy your video editing needs!.
Once you've opened the program, you will need to import your video. Simply hook up your digital camera, locate the video, and voila, the program does the rest for you. It even separates the video into small chunks, based on changes to the video. It is one smart program! You can import other video files, music, or photos all to use in your video. Import everything you will use, and move onto the next step.
Now that you have everything imported, your next step is creating your timeline. Simply drag and drop clips. The program will let you preview every clip to see what is on it. Once you add them to your timeline, this is like adding them to your movie. You can stretch and drag the individual chunks, and this will manage which portions you want to appear on your video. Construct your entire video this way, and you are ready to create some video editing magic.
You will notice two other portions to your video timeline. The first of which is music. If you imported a couple of songs, you can drag and drop them, and this will cause music to play along with your video, which is definitely a nice touch to any movie. The other bar allows you to drop words or pictures on the screen. Click on the side menu which says add credits, and explore all the available options. You can make crazy words do whatever you want to describe the action, or simply point out something interesting. And feel free to create credits at the end of your video.
Finally, your video is in desperate need of a little flare. By right-clicking on any of your video chunks, you can manage special effects between scenes. Fade in and out, flutter the pages, or you can do some interesting things to a scene like making it appear in black and white, or making it look like an old movie camera. Experiment with all the special effects until you create something you love.
When you are done creating your masterpiece, you can preview the whole thing by pressing play. When you are satisfied, you have to save your movie by going to the File -> Save Movie bar. You should see plenty of different options, like saving your movie to play on your computer, or saving it so that you can burn it onto a DVD. Choose which option you'd like, and watch as your movie is created on your computer.
Now you are done! Time to share your movie with the rest of the world, and see what the critics have to say about it!
How To Block Your Cell Phone Number
There might be many reasons why you want to block your cell phone number from showing up on other people's caller IDs. Whatever the reason is, it's very simple to block your cell phone number. You have two options: you can permanently block your phone number or you can block your number on a call by call basis.
Blocking Your Cell Phone Number Permanently:
The most permanent solution is to request a "line block" from your cell phone carrier.
To do this you simply need to call the customer service for your specific provider and they can block your number. When you do this your number will never show up to anyone.
To call your customer service to block your cell phone number, just dial 611 from your cell phone and you will reach them.
If there is a situation where you want your number to show up, you will still have an option. When you have a permanent block on your cell phone number you will need to dial *82 before dialing the number you are calling. When you do this your phone number will show up just once for that specific call. Ex: *82 (555) 555-5555.
Blocking Your Cell Phone Number Temporarily:
Sometimes you may want to block you number for a specific call. You might not want someone to know that you are trying to reach them for the 15th time in a row, or you might be calling a business and might not want them to know your number.
If you want to block your cell phone number on a call by call basis you need to dial *67 before dialing the number. Ex *67 (555) 555-5555.
When you do this you will not have any feedback that it worked. If you want to test this, just call your home phone, or anther phone that has a caller ID from your cell to confirm that your phone number is blocked.
One important thing to remember is that your number will not be blocked from emergency services or any toll free numbers.
Blocking Your Cell Phone Number Permanently:
The most permanent solution is to request a "line block" from your cell phone carrier.
To do this you simply need to call the customer service for your specific provider and they can block your number. When you do this your number will never show up to anyone.
To call your customer service to block your cell phone number, just dial 611 from your cell phone and you will reach them.
If there is a situation where you want your number to show up, you will still have an option. When you have a permanent block on your cell phone number you will need to dial *82 before dialing the number you are calling. When you do this your phone number will show up just once for that specific call. Ex: *82 (555) 555-5555.
Blocking Your Cell Phone Number Temporarily:
Sometimes you may want to block you number for a specific call. You might not want someone to know that you are trying to reach them for the 15th time in a row, or you might be calling a business and might not want them to know your number.
If you want to block your cell phone number on a call by call basis you need to dial *67 before dialing the number. Ex *67 (555) 555-5555.
When you do this you will not have any feedback that it worked. If you want to test this, just call your home phone, or anther phone that has a caller ID from your cell to confirm that your phone number is blocked.
One important thing to remember is that your number will not be blocked from emergency services or any toll free numbers.
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