I've always known that children like mixing things up, of course, they do it any chance they get. I was forever coming up with ways to involve kids in mixing up paints or play dough or volcanic eruptions, but it wasn't until I met Jenny of Let The Children Play fame that it occurred to me that there didn't need to be a goal to their mixing . . . Or at least I didn't have to have a goal.
They have just as much fun, they learn just as much if not more, and I don't have to hang over them bossing them around about measurements, proportions, spillage or waste. In fact, nothing is wasted in free-form potion making.
We just put out, for instance, bowls of flour, Ivory Snow, corn starch, powdered tempera, salt, and sand, along with some cans of shaving gel (they've been on my shelves for at least 5 years, sitting there since a parent bought it instead of the shaving cream I'd asked for), and pitchers of water and vinegar. I've sometimes used vegetable oil and corn syrup as well. And anything else we might have lying about. Add some empty containers for mixing and let 'em go.
We don't start by telling the kids what they were mixing, but rather let them discover it on their own. It's always a surprise when the first child combines the baking soda and vinegar, but when the reaction happens, the ones who already know tell the ones who don't about what's happening, explaining it in terms they will understand.
Then, naturally, they all want to do it. After awhile (and they need at least 45 minutes to really engage in potion making) as the bowls need refilling, they start to ask for ingredients by name ("I need more baking soda," or "I want the shaving cream when you're done.") or ask questions ("What is this stuff?") or try to figure things out for themselves by sniffing ("This is the vinegar!") or touching or looking carefully, as they try to create or re-create results. That, my friends, is science: not following a recipe, but rather inventing or discovering one. I love more than anything else when they don't even bother to turn to an adult with their questions, but instead ask a friend, "How did you do that?" That, my friends, is how community is built and products improved; not by hoarding information to later sell in the supposed "free market."
It's so tempting as a big, all-knowing adult to want to intervene, to show or tell them what we know rather than let them discover it on their own. We worry about clothing, messes, and waste. We see them heading down the tunnel without any cheese and want to take them by the shoulders and turn them around. And, I suppose, there is a time and a place for that, but I nearly always find it's better to just turn learning over to the kids and let them teach themselves.