We have recently discovered three fun, messy, things to do with cornstarch. Even if you hate the messy part keep reading. Cornstarch is remarkable easy to clean up.
1. Side walk paint: I would say about 2:1 water to cornstarch, plus food coloring. Take a muffin tin and measure out the water and cornstarch into each muffin space. Add a couple drops of color to each space. I thought my mixture was too thin resulting in the painting hard to see when the kids were actually painting. But when the water evaporated the paintings looked great. Feel free to add more cornstarch if you want to see the paintings more when painting.
2. Gummy Dough: I would say about 1:2 liquid soap to cornstarch. But we like to experiment with the texture and consistency a bit. It turns out to be like play dough, but shinier, stretchier, and a little gooeyer.
3. Obleek: I would say it is about 1:1 water to cornstarch. Again play with the consistency. Simply mix the water and the cornstarch and get your hands dirty! It is not quite solid and not quite liquid.
Again the clean up is remarkably easy. Cornstarch dissolves very quickly in water. I often have my kids play with the obleek and dough while I am cooking dinner. I set them up at the other end of the counter. The counter is a mess, the cabinets, the floor. With a sweep of the sponge it is off the cabinets and with a quick scrape with a knife off the counters. It is not like flour that gets gluey.