I modified the procedure and got amazing results. To 120 ml water, add 80 grams cream of tartar (kroger brand use). Hold at 95 C in a water bath, adding 1 gram sodium bicarbonate (kroger brand) at intervals until all cream of tartar has reacted. Decant and filter with coffee filter. Pour fluid on ceramic plate. Add 20 ml of 99% isopropyl alcohol 5 times at 10 minute intervals. Let stand under a fan for 1 hour and 30 minutes. Longer may yield larger crystals, however these were sufficient for my purposes. Yield is approximately 90 crystals, 40 of which are large (1 cm or more) and uniform. Crystals have a clear appearance.
Using Sodium Hydroxide as the base instead of Sodium Carbonate, has yielded the bast results for me.

from Homemade Piezoelectric Material