4 tbsp. salt
4 tbsp. water
4 tbsp. ammonia
4 tbsp. liquid wash bluing (Dierberg's has this product)

Mix ingredients. Pour over several small pieces of charcoal or pieces of sponge in a bowl. Put several drops of different colored inks on various parts of it. Leave it undisturbed for a day. Crystals will cover it in an interesting formation, growing and spreading every day. It will be white where no ink was used.