Beautiful Butterflies

Here's a project that combines science and art! First, the instructions...

What You'll Need:
White cone-shaped coffee filters (Melitta-type)
Washable color markers
Scissors
Clear plastic cups
Water

Cut a coffee filter as shown in the pattern at right. When you are done, open it up to make a butterfly shape. Color designs on the wings with markers. You don't have to cover the entire wing, and they don't have to be the same! Don't put colors on the "body" part on the bottom.

Pour about 1/2 inch of water into a plastic cup. When you have finished your artistic creation, shape the filter back into a cone and place it in the cup. The "body" should just be in the water. Sit back for about 10-15 minutes and watch what happens. When the water has reached the top of the butterfly, take it out of the water and let dry.

First of all, you will see the water start to move up the coffee filter. This is called capillary action, and it's the same reason that paper towels can blot up spills. But as the water moves into the areas you colored, you'll see something strange happen. The colors don't stay where you put them! Some of them will move. Others will spread out into weird shapes. And still others will break up into more colors! The final butterfly pattern probably doesn't look anything like what you started with. Why does this happen? Because the inks in the markers are washable, they dissolve in water. So when the water reaches them, they can be carried along with it.

This is an example of a technique scientists call chromatography, which is Latin for "writing with color". Chromatography is used to separate complicated mixtures so that they can tell what's in them, even if the things being separated don't have color. Scientists have all kinds of interesting gadgets that let them "see" things that are invisible!

Can Dogs See Colors?

Actually, it turns out that they can! But they don't see as many colors as we do.

Eye See Colors

So, we have colors from light, and colors from pigments, but how do we see color? Well, with our eyes, obviously, but what is it about our eyes that makes us able to tell yellow from green, fuchsia from teal?

You can think of your eye as a ball; the lens is in the hole that you see through. The back part of the eyeball is called the retina. The retina contains a lot of cells. Two kinds that are important in color vision are the rods and cones. Your retina contains about 120 million rod cells and 6 million cones! Rods don't actually see color, but they help you know how light or dark something is, and if it is moving. There are three types of cones - those that sense red, blue, and green light.

Some people have problems with their cone cells, and they find it hard to tell colors apart. For example, red and green might look very much alike to them. This is called color blindness. Do you know anyone who is color-blind? If you do, that person is probably a male, because males are 16 times more likely to be color-blind than females!

Create a Color!

Some weeks ago, we talked about how white light is composed of all the colors of the rainbow. You can use a prism to separate white light into red, orange, yellow, green, blue, indigo, and violet. If you had a way of combining the colors again, you'd recreate the white light.

Have you ever tried mixing paints or food coloring to get different colors? You can combine red and yellow to make orange, blue and red to make purple, and blue and yellow to make green. But what if you mix all the colors together? If the paints acted like light, you would make white paint! But that isn't what happens at all (try this if you haven't already). In fact, you get a yucky grayish-black color. So why do the paints act different from light?

Remember that we talked about why objects appear to be different colors - they absorb all the waves except those that create the color you see. The same thing happens with paint. When you mix them all together, they end up absorbing almost all the waves, and that makes the paint mixture appear grayish-black. This is called subtractive mixing because waves keep being removed when colors are blended.

The colors in light behave different. They mix in an additive way. Red light only has waves that appear red, and blue light, waves that look blue. When you mix them together, you get waves that look pinkish-purple (a color called magenta). Not surprisingly, blue and green make a sort of turquoise (cyan). But when you mix red and green, you don't get some ugly brownish color - you get yellow!



Yellow??!!?? This is hard to believe. You can actually play with additive color on your computer. Open up a program that lets you mix your own colors. For example, you computer probably has a program called Paint or MacPaint. You may need someone who can use this program to help with this (you can do the same thing in Word or PowerPoint). Draw a square or other shape, fill it with the paint bucket tool, then find a way to create "Custom Colors". You'll see boxes labeled "Red", "Blue", and "Green". Put various numbers in to see what result you get. You can also adjust how light or dark the color is. Can you invent a new color? What will you call it?