Magic Color Chalk in 3 Steps

Materials you'll need

• Several colored chalk sticks (at least 3–4 colors)
• Note card or index card
• Tall glass filled with cold water
• A butter knife or similar blunt tool for shaving

 

Step-by-step tutorial

Step 1: Hold a note card flat on the table. Using a butter knife, shave each color of chalk over the card, creating separate small piles of chalk dust — one pile per color. Ask a grown-up to help with the knife if needed.

Step 2: Set a phone on a flat surface with the flashlight turned on. 

Step 3: Place a glass filled with cold water over the light. Pick up the card and gently tip the chalk dust onto the surface of the cold water, pouring all the colors in at once. Watch as the chalk dust spreads across the surface of the water, creating swirling bursts of color. The chalk will slowly sink as the colors disperse.

Learn more

When you shave colored chalk and pour it onto cold water, the chalk doesn't dissolve — it forms a suspension, meaning the tiny solid particles spread through the liquid without actually breaking apart into molecules. Chalk is made from a mineral called calcium sulfate (or calcium carbonate), which is barely soluble in water. The vivid colors come from dye pigments mixed into the chalk and because those pigment-coated particles are less dense than water at first, they spread beautifully across the surface before slowly sinking.