Baking Soda Stalagmites And Stalactites
Baking soda is a good material for growing homemade stalagmites and stalactites. The non-toxic crystals form quickly and show up well against a dark-colored yarn. It's easiest to use gravity to get crystals to grow downward (stalactites), but constant dripping from the center of the yard will produce upward growing crystals (stalagmites), too.