Recommended by Debra Immergut and son, Joe, age 11
Science experiments are commonplace in our house, where my son has filled an attic "lab" with mysterious shampoo-based potions sealed in old jars. But few of these projects, Joe and I agree, have been as rewarding as the crystal-tree propagation we tried not long ago. Making the cardboard bases and setting them in a salt solution took just a few minutes. A day later, we were astounded by the mass of tiny crystals forming along the tree's branches as the cardboard wicked up the solution. Two days later, we had a tiny enchanted forest, each tree fat with bristly spikes. Joe's lab report: "It was worth the wait — it was amazing!"
To create the base, cut two cardboard tree shapes (about 4 inches tall and 3 inches across at the widest point). Cut a 2-inch slot in the top of one shape and in the base of the other. Join the shapes at the slots and stand the tree in a deep saucer or a small bowl.
In the jar, combine 1 tablespoon water, the salt, bluing, and ammonia (handling ammonia is a parent's job). Fasten the lid and shake well, then pour the solution into the saucer or bowl.
Leave the tree undisturbed. Crystals may take as little as an hour or as long as a day to begin to form, depending on the humidity in your home (they'll grow better in drier air). The tree will keep growing over the next few days, until all of the liquid evaporates.