Ask any person beyond first grade, “What is the number of primary colors?” and all will agree that there
are three. Asking, “What are those colors?” in a group of people and usually you’ll hear, “red, green,
blue and yellow!” Scientists and artists have long argued over the question of whether yellow and
green are actually primary colors. Sometimes this issue is “resolved” by discerning the colors of light,
or additive primaries and the colors of pigment, sometimes called subtractive primaries. Students are
forced to “choose sides” or remember different rules for different circumstances. Rather than focusing
on the differences between the arguments, I choose to dwell on what all agree on—that there are three
primary colors and ask my students to operationally define what it means to be a “primary” color.
Soon they argue that primaries are the ones that make up all other colors and ones that cannot be
made by mixing other colors. Whether working with adults, adolescents or young children, these two
concepts always seem to be put forth and mutually agreed upon. Keeping this definition in the back of
their minds, students are asked to participate in an investigation designed to combine colors in a novel
way—to paint with light.
The materials we use are depicted in Figure 1. The red, green
and blue light sticks and plastic pipettes (medicine droppers)
can be easily purchased online. The paper plates and cotton
swabs were purchased at a grocery store, and the red PVC
cutter was purchased at a local hardware store. Additionally I’d
have lots of paper towel on hand. The light sticks are
ingeniously created by enclosing chemical “A” inside a fragile
glass tube that is bathed in chemical “B” which is enclosed by a
flexible plastic tube.
Bending the tube breaks the glass tube and mixes chemicals “A” and “B” thus producing a chemical
reaction that results in energy being released in the form of either red, green or blue light. The teacher
then uses the PVC cutter to cut off the top of the soft plastic container revealing a tube of “light” for the
students to investigate. In high school, and working with adults, we use the remaining tube as a test
tube from which to draw the light. At lower grades or with students who might find the operations
taxing, I’d suggest pouring the liquid through a filter, to remove the broken glass, into a wider plastic
container. Place a plastic pipette in each of the three colors and students are ready to mix colors and
creatively apply their understanding.
I ask my students to create a puddle of each of the three colors on a paper plate and then stir with a
cotton swab. The swab absorbs the color quite nicely and becomes the norm for each of the three
colors. Then students create a puddle of a combination of red and blue, another of blue and green and
then one of red and green. Using a different swab to mix each combination students soon see that the
combination produces, in each case, a brighter color. They are asked to arrange the swabs in “a
meaningful way” which allows them to visually display their understanding of the color combinations.
STEAMed Magazine
7
April 2016 Edition