Have you ever gotten ink writing wet and discovered that your black ink is actually composed of shades of purple or brown? That’s what candy chromatography is-an experiment designed to separate the colors in a candy shell to see what dyes were actually used to create the color.
The roots of the word chromatography are chroma, meaning ‘color’ and graphein, meaning ‘to write’. Color writing is a method used to discover what unknown substances are, such as blood or drugs at a crime scene.
It’s used in process monitoring to make sure that a substance, such as a drug compound, is being produced in a pure form during the manufacturing process. Candy chromatography teaches the process of chromatography and is a popular science experiment, using easily available materials.
It works because the separate elements of a complex solution will differ in how much they stick to things. Different materials are used in chromatography, but they will generally have a mobile phase and a stationary phase.
In paper chromatography, which is the method used for candy, the mobile phase is the water and the stationary phase is the paper. The dye is dissolved in the water, and the components of the dye will separate as they go through the paper. Some components will stick to the paper faster, while others will be less sticky and spend more time in the water, thus traveling up the paper farther.
There is some disagreement in the experiments as to how to get the candy coating off of your M&Ms or Skittles. Some experiments state that the coloring can be removed by placing them in water-others say that you need vinegar or even heating to remove the coating. All of them say you should stop dissolving the candy after it becomes white.
Coffee filters are often used for the paper. Dot the coffee filters with the dye you removed from the candy. Cut into squares, with a dot from a different color on each strip of paper. You need a solution (your mobile phase) to separate out the colors-use a 1 % salt solution and place the paper in a jar with the solution at the bottom. The water will magically climb the paper due to capillary action.
The colors of some candies have more than one dye in them, and will separate into bands. The dyes will end up at different heights on the paper. After drying them, you can try to see if you recognize the color of the candy that you used, or whether the candy had one color of dye or more, or if different candies of the same color ended up at the same level on the paper.
You can easily find detailed instructions for this experiment on the internet and in science books. It’s a fun way to learn about an important scientific process that is used in practical applications every day.