Whether you call it slime, flubber, oobleck, goo, goop, gak, gunk, ooze, putty, or play dough, we are talking about gooey, homemade polymers that can provide both hours of fun and an introduction to chemistry.
Despite the title, I don't think we're talking crafts for babies here, but rather toddlers and preschoolers. Stephanie Brown's simple craft recipes include modeling goop (made from salt and cornstarch), bread play dough (made from white bread and a bit of white glue) and cornstarch clay. Feelie bags (made with zip lock bags and colored hair gel!) are a mess-less tactile treat for toddlers. Close them with duct tape to reduce the possibility of an explosion.
Anne Marie Helmenstine, Ph.D. is About.com's chemistry guide. But you don't need a Ph.D. to follow her recipes for a bouncing polymer ball, electroactive slime, fake snot (eww!), Metamucil flubber, or glow-in-the-dark slime. I was fascinated by her illustrated Floam recipe. "Floam is like slime with polystyrene beads in it, that kids can mold into shapes. You can sculpt with it or use it to coat other objects. You can store it to reuse it or allow it to dry, if you want permanent creations."
Non-Newtonian fluids sometimes behave like liquids and sometimes like solids, thereby defying easy categorization. Quicksand, gelatin, and ketchup are a few examples of non-Netownian fluids. So is the slime recipe presented here, along with explanations of some of the science principles at work. "The thing that makes this particular slime work is the bonding of polyvinylacetate (PVAC) molecules by the Borax (sodium tetraborate). The molecules (polymers) are long to begin with, and they are tangled, which is why the glue is so viscous."
Normally I visit Cooks.com for dinner recipes, so I was pleasantly surprised to find that they also house dozens of recipes for slime, silly putty, goop, and play dough. Simply use the search box to find them. Most of these slime and putty recipes are just for play, but you will find edible treats (such as Green Slime made with lime Jello, lemon pudding, evaporated milk and soda crackers) hiding among the craft recipes.
"The Slime we made is just a demonstration of how certain polymers are effected by other chemicals, such as 'cross-linkers' . Polymers are used in nearly everything these days, such as most kinds of plastics, nylon, and clothes. You can sometimes spot a polymer by it's name: if it ends in -on, like nylon or rayon, it can be a polymer." This page from Household Science for Kids has one slime recipe and a good explanation of the science behind it. You'll find another recipe at their Iso/Thixotropy page.