A fun science activity, crowd-pleaser, and perfect boredom buster: sidewalk paint rockets that burst colorful chalk paint onto the pavement and wash away easily with water.
We made a whole rainbow and had a blast launching them, decorating the backyard sidewalk as the rockets exploded into colorful splatters. Friends joined in, and everyone loved the mess and the science behind it.
We’ve made sidewalk paint with cornstarch, water, and food coloring many times. When you add an antacid tablet and trap the resulting gas inside a small container, the pressure builds until it launches the container — creating a quick, safe “rocket” effect. This simple idea is a favorite for kids’ magazines and at-home experiments.
Follow the steps below to make your own sidewalk paint rockets.
Sidewalk Paint Rockets
Supplies:
- Antacid tablets
- Cornstarch
- Film canisters
- Food coloring
- Water
Step 1: Add 2 drops of food coloring to each film canister, then add about ½ teaspoon of cornstarch.
Step 2: Fill the canister with water until it is about one-third full, and stir to mix the cornstarch and color into a paint-like consistency.
Step 3: Break one antacid tablet into three or four smaller pieces. Use roughly one full tablet (broken up) per canister.
Step 4 (launch): Place the canister on the ground in an open area with plenty of clearance. QUICKLY add the antacid pieces, snap the lid on, turn the canister lid-side-down on the ground, then step back or run to a safe distance.
The gas created by the reaction will build pressure and launch the canister into the air, leaving a colorful starburst of paint on the pavement. It’s addictive — once you launch one rocket, you’ll want to keep going until your sidewalk looks tie-dyed.
Cleanup is simple: hose the sidewalk with water to wash away the cornstarch paint once you’re finished playing.
Try different color combinations and spacing to create layered bursts and patterns. This is a great activity for small groups, summer playdates, or outdoor learning sessions that combine art and basic chemistry.
You might also enjoy other antacid tablet science experiments for more fizzing, bubbling fun.
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