Explain to students that certain dyes have colors because they absorb some colors from the light while not absorbing others. The colors that students see are not the colors that the dye absorbs, but instead the reflected light that enters their eyes.
Have children put shaving cream in a bag. Add different colors to the bag, close it and push on the shaving cream. The children can observe the colors change as they mix together. Have the child predict what color the shaving cream will become before adding a particular food dye to the shaving cream. Ask the child if the shaving cream turned into the expected color.
Put shaving cream in a plastic bottle that is halfway full of water. The quantity of the shaving cream does not matter. Add drops of food dye so that children can observe how water, shaving cream and food dye mix together. Mixing shaving cream colors is especially helpful when children have a difficult time remembering what colors create when mixed together or when learning colors in general.
Children can use shaving cream and food coloring to engage in paper marbling. The process of paper marbling can create a design similar to marble. Paper and shaving cream interact with each other because paper contains cellulose and shaving cream contains soap, which interact to produce a marbling effect. Fill a cup half full of water and add a drop of food coloring. Spray shaving cream on the plate. Use a spatula to flatten it out and make it larger than the paper. Add five drops of food coloring to the shaving cream. Use a toothpick to create patterns in the shaving cream. Press sturdy paper on the shaving cream and scrape the shaving cream off from the paper. Look at the impression and write down what you see. Mix the shaving cream on the paper and add food coloring if it doesn’t have enough color. Add a drop of water to the shaving cream and write down what happens. The paper should look swirly and reminiscent of marble materials.