2.1.12

Test Tube Science: Mouse Paint


Materials:
   -Five test tubes
   -Food coloring
   -One pipette

Background:
We got this idea from the book called Mouse Paint by Ellen Stoll Walsh. My son had a test tube rack with all the primary and secondary colors on it and would talk about them and to them almost everyday between the age of 18-36 months.  He learned his colors really well and has been able to tell what will happen if you mix different colors because he practiced so many times

Directions:
 Fill four test tubes with water.  Into each, put one drop of food coloring (use red, yellow, and blue).  Stir carefully by tapping your finger on the test tube.  Pour half of one color into one of the empty test tubes.  Pour half of another color in on top of it.  Stir carefully.

What makes purple?  _________________+____________________

What makes green?
 _________________ +____________________

What makes orange?
_________________+_____________________

4 comments:

D said...

I think your idea about mixing primary colors for kids in test tubes is great!
I think kids should be taught a little more clearly about the primary colors than we usually are, though.

Additive color space looks something like this:
http://www.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/CIE1931xy_CIERGB.svg/325px-CIE1931xy_CIERGB.svg.png&imgrefurl=http://en.wikipedia.org/wiki/CIE_1931_color_space&h=345&w=325&sz=40&tbnid=EkYw_LbmADWVaM:&tbnh=90&tbnw=85&zoom=1&docid=SKRQ9HbFToIhFM&sa=X&ei=PWb8TrelEcfY0QGal8GgBw&ved=0CEYQ9QEwAw&dur=381

You can see that the hues are basically arranged radially, tending towards white in the center. Subtractive color space is the same, but with black in the center. This means that any three colors which contain the center white point within their triangle can be considered primary colors, because they fit both of these criteria:
1. A primary color cannot be derived from mixing other colors together.
2. The primary colors can be combined to make all hues.

In particular, Red, Yellow, and Blue are a set of primary colors.
However.

The purple and blue-green formed by mixing these colors is very dark. If you want a strongly saturated, bright magenta or cyan, there's no way to get it by mixing these three colors.
On the other hand, mixing magenta and yellow can in fact produce a very nice red pigment. And mixing cyan and magenta makes a perfectly good blue pigment. By mixing with a little black you can also get the dark magenta and dark cyan that one could get mixing red, yellow, and blue.

What this amounts to is that the best primary colors, the ones able to produce the widest range of colors, are yellow, cyan, and magenta. These mix to form red, green, and blue.
So why do we say that red, yellow, and blue are the primary colors? Well, if you look at a print cartridge and you don't know the proper terms, you would probably call cyan a type of blue and magenta a kind of red. More fundamentally, the cells in the eye respond to four kinds of hue: Red, Green, Yellow, and Blue. So in a way these are the most intense sensations, and they act as attractors to color names.
Notice that cyan and magenta are very bright colors. Mixing two bright colors always gives a darker color in pigment space.

So I say children should be taught in preschool that cyan, magenta, and yellow are the primary colors, and these mix to form red, green, and blue.

(There's a little more to it than this. You see that the color space is not in fact triangular, but has a curved edge. To get colors outside the CMY triangle, you can introduce colors and mix a tiling of this color space by triangular regions. But this is probably too complex to teach at the preschool level.)

D said...

Here's a picture of me learning about mixing colors as a 4th grader.

D said...

Here's something else to think about: If you could have colors go into the negative, you would only need two colors to span the hue space. In the LAB color model, these colors are called A and B, and correspond to Red-Green and Yellow-Blue color axes. (The L stands for Luminosity and corresponds to the bright-dark axis.)

David Stay said...

D-
Thanks for the comments. The picture of the science project is great. I love that many of our science projects weren't as highly refined in the presentation portion but had awesome bits tossed in like power tools.

I use the CIE 1976 http://en.wikipedia.org/wiki/CIELUV color space to describe the emission of my polymers. I hadn't thought about multiple primary colors before, I knew they existed but I hadn't thought about what it took to be a primary color.

I'm using RGB because that is what the most common food colors come as. If you try it one thing you may notice is if left in the window sill the purple will slowly shift red because the blue is absorbing higher energy light and breaking down faster.