How to Grow a Crystal

Pick up some alum from the spice and flavoring section of a local supermarket or grocery store. You'll need at least 4 ounces.

Heat a small pan filled with a cup of water to about 122 degrees, an optimum temperature for alum solubility, according to Princeton University. Check temperature with a thermometer. Pour the water into a clean beaker or tumbler.

Stir 2 ounces of alum into the water until dissolved. Place a sheet of paper or coffee filter over the top of the beaker. Find a clean, dust-free indoor location for your crystal growing. Avoid areas with heavy vibrations, such as laundry rooms. Leave for a few hours or overnight.

Tie a length of thread to the center of a pencil. Choose a pencil that fits across the top of the beaker, and a length of thread that reaches the bottom of the container, with a little extra for tying.

Take the cover off the beaker and gently decant the solution into another clean jar or beaker. Pick out any crystals that form at the bottom of the container. Tie the largest crystal to the thread attached to the pencil.

Smear a little cooking oil on the thread above the crystal to stop the crystal growing along the thread. Heat up the remaining alum solution from the previous beaker to around 122 degrees. Allow it to cool. Suspend the crystal in the solution by balancing the pencil on the beaker rim. The crystal should be submerged in the solution.

Cover the top with paper and leave the crystal for a week. Check back to see if the smaller seed crystal develops into a larger form.