Chromatography & Experiments with Color

 Hi Families,

We decided to have a little fun with candy and color. We know that certain pigments in paint and food dye are required to make all other colors: these are red, yellow and blue. When 2 of these primary colors are mixed, we achieve secondary colors: green (blue + yellow), orange (red + yellow), and violet (red + blue).

For this lesson, we experimented with the science of chromatography, where parts of a mixture are separated by allowing it to travel through a material that will absorb each part at a different rate. "Skittles" were placed at the bottom of a strip of filter paper that had a bit of water at the center. The dyes slowly released from the candy and moved their way up the paper. We waited an hour to observe the results (which are very, very subtle). Dexter, a 2nd grader, was the first to identify the separation of colors in the green, orange and purple candies. Do take a close look at the photos below to see if you can identify what other colors were present in the dye. Note: the red and yellow candies remain red and yellow without color separation, because these are primary colors : )

Our collection of samples

Look where the orange color borders the white of the filter paper: what color do you see?

Look closely along the edges at center... what color, other than green do you see?

 

No color separation here: red is a primary color

This is hard to see: there is a touch of blue that separated from the purple

The photos you see below are from "Nerds" candy. Again the results are very subtle, however you can detect a touch of color separation.

Look for hints of blue

What colors do you see "bleeding" from the green?

No color separation here. Do you remember why?

No color separation here either. Yellow is a primary color.

Below, we conducted a similar experiment with different brands of black markers. Not all black dyes are formulated the same way and their pigments may vary. We drew a circle and filled it in with a black permanent marker, a black "pip squeak" marker" and a "crayola" marker. The permanent marker does not dissolve in water, so there was no change. Can you identify what colors separated from the dye of the other 2 markers?

3 different brands of black marker

Here we tried the same experiment with different marker colors. Can you identify specific another color or colors that make up the main color?

main color: teal

main color: orange (hint: look closely at the edges)

main color: purple

magenta does not separate. why?

The following day, we made paintings on the coffee filters.  There is something really special about leaving the common shape of the rectangle and working within a circular shape. Students experimented in a number of ways, folding the paper, spraying it with water and working with watercolor and diluted tempera paint. You can see the different approaches below. They are fabulous!!!