This fizzy sidewalk paint is a fantastic upgrade over standard chalk on the sidewalk! Thanks to good old baking soda and vinegar, your kids can have some STEM fun watching the bubbly reaction.

To make the paint, I stirred together one (16-ounce) box baking soda, 1/2 cup cornstarch, and 1 cup warm water. Stir until well combined, then divide among plastic cups and add food coloring to each. The colors didn’t come out as rich as I hoped, but we had enough pigment to show up on the pavement, which was all that mattered.

We headed outside on a very hot afternoon, and started making designs. I showed Veronika a few examples of letters and shapes, while she painted something decidedly more abstract. Older kids can make as complicated a picture as they like!

But now for the real fun: once the paint is down, use a squirt bottle filled with white vinegar and spritz over your artwork. Note: An empty mustard bottle with the cap on works perfectly; simply squeeze and dispense a little vinegar at a time.

Every time the vinegar hits the paint, foamy bubbles ensue! This was such fun for Veronika to observe.

As a bonus, this paint washes off like a dream. Simply use a watering can to rinse everything off, and the clean up becomes part of the play.