It's to Dye For!

This experiment is very messy, so be sure that you have an adult's permission to do it, and that you spread lots of plastic, newspaper, or other kind of protection. It's also a good idea to wear rubber gloves, because these dyes can stain your hands. The dye will eventually wear off, but it may take a few days!

What You'll Need:
6" x 6" square pieces of plain white cotton cloth (an old white sheet works well)
Plastic zip-top bags (sandwich size)
Hammer or mallet
Plastic cups
Strainer or cheesecloth
Tongs or tweezers
Pot holder
Rubber gloves
Microwave oven
Water
Deeply colored plant materials, such as tea leaves, coffee grounds, spinach, red cabbage, berries, carrots, onion skins, turmeric (a spice), nut shells, or flowers

Put each plant matter into a plastic bag, zip the top, and mash the material with the hammer or mallet. Carefully open the bag, and pour the contents into a plastic cup. Don't fill the cup more than one-quarter full with plant material. Add water so that the cup is one-half to two-thirds full (use more water, the more plant material you have).

Put the cup into the microwave oven and heat on high for 10 minutes. The water should take on the color of the plant matter. Carefully remove the cups from the microwave (they will be VERY hot!). Using the tongs or tweezers, slowly place a piece of cloth into the solution. Make sure that it sinks down below the surface. Put the cup and cloth in a safe place and let it sit overnight. Repeat this process for any other plant materials you want to experiment with.

Put on your rubber gloves, and remove the cloth from the dye solution. Take the cloth to the sink and squeeze it. Then rinse under cool water. Has it taken on the color of the dye solution? How dark is it? Place the cloth somewhere that it can dry without getting too hot (don't put it in the clothes dryer). Does the color get darker or lighter when the cloth dries? Store your dyed cloth pieces where they are exposed to light. Does the color stay the same, or does it change?

A Law Against Purple!

A few weeks ago, we learned that things around us absorb certain colors of light. So, a tomato is red because some molecules in its skin absorb every color but red. Grass looks green because it contains some molecules that absorb every color but green. But what are these mysterious molecules?

Molecules that have strong colors are called pigments or dyes. There's technically a difference between them, but that's not important right now. There are natural pigments, like the colors found in the tomatoes and grass, and synthetic (artificial) ones. Most of the coloring agents used today are synthetic, because they come in more colors, are stronger, and last longer. But these artificial dyes were first invented in the late 1800's, so for most of human history, people used natural dyes. A lot of these came from plants, such as flowers, nuts, and berries. But some dyes came from surprising places. For example, the dye called Tyrian purple comes from snails that live in the Mediterranean Sea (can you find this sea on a map?). It was very rare and expensive, and in ancient Rome, only the rulers were allowed to wear that color! Can you imagine it being against the law to wear purple?

In the next experiment, you'll learn how to color cloth using natural dyes. But unless you have some Mediterranean sea snails as pets, you probably won't be using any Tyrian purple!

The Color of Things

OK, so white light is made up of many colors. But that doesn't explain why different things appear to be different colors! Why is grass green, if it's lit by white light? Why are tomatoes red? Why are dandelions yellow? Look at all the colors of things around you right now. Why do they look different, even though they're all being lit up by white light?

When white light hits an object (as the light must be doing if you can see the object), the light bounces off the surface toward your eye. This is called reflection. We usually think of reflection in terms of mirrors or other shiny surfaces, but even dull surface reflect a little bit. But (and this is a big but), not all of the light gets reflected. Some of it is absorbed by the molecules in the object, and you only see that colors that do not get absorbed. So, if you're wearing a red sweater right now (as Dr. B is), the only color that is reflected is red. There's a green book on my shelf - what color of light is reflected from it? What about from my blue coffee mug? You get the idea!

But what about things that are white? And how does black fit into this? White objects reflect all of the light toward your eye; nothing is absorbed. Black, on the other hand, absorbs every color, and nothing gets reflected from it.

Who's Roy G. Biv?

Most of the light around us is white (really, colorless) light. But white light is actually composed of many different colors - in fact, it is made up of all the colors of the rainbow, quite literally. A rainbow appears when light passes through tiny rain droplets left in the air; this usually happens after a rain shower.

Where else can you see rainbows? Well, as this picture of Niagara Falls shows, rainbow can also appear in the mist around waterfalls (those little water droplets again!). Sometimes things made of glass or crystal can also break light up into its many colors. You can also see rainbows on the surfaces of CD's or DVD's (the unlabeled side).

The colors in a rainbow always appear in the same order, starting from the top: red, orange, yellow, green, blue, indigo (dark blue), and violet (purple). Many people remember the order of the colors from the made-up name "Roy G. Biv". But in England, they remember, "Richard of York Gave Battle in Vain", which seems awfully complicated. See if you can make up a sentence in which the words start with the letters R, O, Y, G, B, I, and V, in that order.