Yesterday afternoon we experimented with goop! Start with 1/2 c. cornstarch in a bowl. Add 1/4 c. colored water and squish together. Add more cornstarch or water to get a consistency you like. It should be a solid when you handle it, and then turn back to liquid when your hands let it go. The good news? It kept the boys’ attention for a good half hour and it washed right off the driveway!