As a fun little activity to go with our Jesus Walks on Water lesson, we made a cornstarch-water mixture for the kids to simulate walking on water. If you mix cornstarch and water in the right proportions, you’ll get a non-Newtonian fluid. If you lay your hand on it, it will sink in and feel like a fluid, but if you use force against it (like punching or stomping on it), it acts like a solid. So…if the kids walk quickly across the fluid, they won’t sink in at all.
Above, you can see us mixing it up before church. I cleared out an under-bed storage bin. It was shallow and long enough to get a few steps in, plus we could put the lid on until we needed it. We found that the easiest way to mix such a large amount was to start with the water (tinted blue), sprinkle the cornstarch evenly over the water, and mix with our hands. If you try to use a spoon, the resistance becomes too great.
The amount we used in our container was approximately 2 gallons of water, plus 15 (1 lb.) boxes cornstarch. You may have to adjust the amounts, based on how your fluid is behaving. If it’s too watery, add more cornstarch. If it’s too powdery, add more water. Here are our empty boxes:
And here is a link to a short video we filmed, which demonstrates the effect. It’s pretty awesome!
To make it work in the classroom setting, we put the tub on a tarp to contain the mess. Kids took off their socks and shoes and an adult helped them walk across, one at a time. At the other end, another adult had a bucket of water and paper towels and assisted the kids in cleaning up their feet. We left the tub open to allow the water to evaporate and will discard the cornstarch later. Once the spills on the tarp dry, the powder can easily be swept/shaken off.