In a medium-sized mixing bowl, add the cornstarch. Gradually pour in the water, starting with about half of the 1/2 cup.

Begin mixing the cornstarch and water with your hands or a spoon. It will be tricky at first! Continue adding the remaining water slowly, mixing until you reach a consistency where it feels firm when you squeeze it but flows like a liquid when you release your grip.

If you're using food coloring, add a few drops now and mix thoroughly. Be aware that food coloring can stain, so consider wearing old clothes or an apron.

Test your oobleck! Try punching it quickly – it should feel solid. Then, let your fingers sink into it slowly – it should feel like a liquid. If it's too dry and crumbly, add a tiny bit more water. If it's too watery, add a little more cornstarch.