All you need is a cup of cornstarch and half a cup of water with a little food coloring in it (purple and green are fun for Halloween and red would be gross!) Mix the two ingredients to a medium-size bowl with a spoon or your fingers. The goo should be the consistency of syrup.
Now, play with the mixture! You will discover that it behaves like a solid when you agitate it, or move it quickly, and like a liquid when you let it sit still. Pour some onto plates or into bowls if you want to. We poured it directly onto our table which was pretty messy, but lots of fun! Hold a handful on your palm and watch it drip between your fingers! Roll it into a ball. If it gets too dry, just add a little more water. You can easily clean the goo off of flat surfaces using a plastic spatula. Wash it off hands with water.
Cornstarch molecules are like long ropes. When you leave them alone, or move them slowly, they can slide past each other and look like a liquid. However, if you squeeze them, stir them or roll them around in your hands, the ropey molecules look and feel more like a solid. Materials like cornstarch goo are known as non-Newtonian fluids, since they don’t have the normal properties of either a liquid or a solid.
Click here to watch my video on how to make cornstarch goo.
Mad Scientist’s Green Slime is a homemade polymer that’s as much fun to play with as it is to make. Here’s a demonstration I did on our local morning show: Halloween Science on Kare 11 Sunrise show (It will start playing on the right side of the website after a short ad.)