March Moment of Science:
Mixing & Separating Colors

How is the color green made? Is black really black? These types of questions about colors can be explored through these two experiments, where primary colors are mixed together to form a secondary color and all the colors that make up the color black are separated from each other.

First, gather your materials:

  • Snack or sandwich size Ziploc bag
  • 3 – 4 tablespoons light corn syrup
  • Blue and yellow food coloring (can also use red)
  • Cotton swab or craft stick (optional)
  • Cardstock (optional)
  • Short cup half filled with water
  • Thick coffee filter (such as Chemex brand)
  • Scissors
  • Water soluble black markers
  • Pencil
  • Non-water soluble black markers (optional)
  • Paper towels

Then, follow these instructions:

1. Color Mixing

a. Pour about 3-4 tablespoons of light corn syrup into the Ziploc bag.
b. Slightly flatten the bag so the syrup is spread from one side to the other.
c. Add two drops of yellow food coloring to one side of the bag.
d. Add one drop of blue food coloring to the other side of the bag.
e. Tightly seal the bag; then use your fingers to mix the colors and the corn syrup together. What color do you get when you mix blue and yellow together?
f. If you want, you can use this as paint, using a cotton swab or craft stick and a piece of cardstock to make your own work of art. Note: the corn syrup never fully dries, so you can use contact paper or a spray-on sealant to preserve your artwork and hang it on a wall!

2. Separating Colors

a. Cut the coffee filter into a circle (make sure the diameter is larger than the opening of the cup you are using).
b. Use one of the black markers to draw four large dots near the center of the circle:

Moment of Science_March

c. Using the pencil, poke a hole in the center of the circle (inside the black dots).
d. Tightly twist a strip of paper towel into a wick and stick the twisted end of the paper into the center hole of the filter paper. The filter paper disk should now resemble a small umbrella.
e. Place the filter paper on the rim of the cup so that the wick is touching the water inside the cup.
f. Watch as the paper towel wick soaks up the water and starts to spread across the filter paper. What is happening?  This step may take a while, so be patient; it is worth the wait!
g. Once the water spreads about ¾ of the way toward the edge of the filter paper, carefully lift the disk out of the water, pull out the wick from the underside, and lay your paper some place safe to dry.
h. Optional: try this experiment again, using a different brand of water soluble black marker. How do the colors that make up the two different markers compare?  You can also try this with non-water soluble markers – what happens?  Do you think these markers will dissolve in something other than water?

Color Mixing – What happened when the yellow food coloring mixed with the light corn syrup? The food color turned the corn syrup yellow as well. As the yellow and blue corn syrup began to mix together, a new color was formed – green! Yellow, blue, and red are all primary colors. When two primary colors are mixed together, a new, secondary color is formed. Yellow and blue together make green, and yellow and red together make orange. Can you guess what color blue and red make when they are combined together?

Separating Colors – What is happening? Is black really black?  Black is actually made up of a lot of different colors mixed together.  In fact, there is a rainbow of color hiding inside just one black dot.  The burst of color that you see on your filter paper proves that black is really a combination of colors. This technique of separating colors is called chromatography. As the water soluble black ink dissolves in the water and moves in between the fibers of the paper, it is separated into bands of color. Different colors get carried faster and farther than others because some molecules are bigger and heavier than others.