I found an old recipe for green slime while I was cleaning out some drawers, so I planned on doing it the next day. The recipe I found called for 1 cup of cornstarch and 1 cup of water, plus some green paint. If you've made this before, you can probably already see the mistake. With that amount of water, all we made was - watery guck. Nothing interesting.
So Kay and I played around with it, dumping water, adding more cornstarch, adding a little more water, until we had something workable.
And we skipped over the green paint entirely, with Kay mixing colors until it was a pastel pink (not the icky-brown she usually comes up with!). It was still watery in the end, but she was able to play with the cornstarch that clumped on the bottom.
When she was done playing with that, she took up the nearly-empty red bottle of paint and made "chicken pox" spots on her arms and cheeks. I had long since decided she was going to need a bath after this anyway, so I let her decorate herself, saying, "Oh, those spots are bad. You should see a doctor!" which she thought was hilarious.
My initial overall opinion of this cornstarch slime, mistakes aside, was that I will never do it again. The cornstarch gets everywhere and even after rinsing it off with a hose, thinking I had gotten it all, it would dry and leave marks on the bricks. Irritating. Next time we use this particular ingredient, we will do it in the grass, where it won't show so much. Also, I absolutely hated the feel of this stuff, but, most importantly, the 4-year-old loved it. And as far as things like this go, anyway, her opinion wins out. So no matter what I say now, I'm betting you will, in fact, find us trying this again in the (hopefully not too-near) future.