Side walk spray chalk... 1. Add cornstarch to one cup of hot water whisking to mix so that there are no clumps. 2. Add one teaspoon of washable tempura paint and a quirt of dishwashing liquid. Mix well. 3. Pour it into your squirt bottles and shake well. Watch your kids enjoy making designs and pictures on your driveway. I always spray my driveway down when we are done. After you let your spray sit a while it will separate. Shake it really well before you use it each time.