> If your kids are old enough to be trusted not to eat the experiments, copper sulfate (used to kill roots that are growing into sewer lines) makes beautiful cr

> If your kids are old enough to be trusted not to eat the experiments, copper sulfate (used to kill roots that are growing into sewer lines) makes beautiful crystals. It can be found at Home Depot-type stores. I had a chemistry set as a kid, it had copper sulfate. The only crystals I've managed to grow :)