I try to have a project for my Grandkids and I to do frequently. The latest choice was making crystals for fun and would also be educational regarding molecules. I bought a five pound tub of Alum and 5 large flat bottom, glass globes.

The sites I found online sounded very easy. Well, I have used about 3 cups of the Alum and have been unsuccessful with each attempt. Nothing forms on the glass after two days. The 'Seed' crystals form on dental floss but when added to a new batch to 'grow' - - they just dissolve. The water is supersaturated with alum and will hold no more. What am I doing wrong?
Sue