Historically, bluing was used in laundry processes to make clothes whiter. It is a "colloidal suspension" made of a fine blue iron powder suspended in water. A pH balancer and a biocide are usually included to prevent the buildup of algae and bacteria and bluing is nontoxic, biodegradable, non-hazardous and environmentally friendly. In the crystal forming investigation, it is the tiny particles ferric hexacyanoferrate in the bluing that contributes to crystal formation. As the water from the bluing evaporates the ferric hexacyanoferrate can no longer stay in solution. The salt crystallization process will take place around the blue particles as nuclei. Ammonia is added and speeds up the evaporation process. Adding more bluing and salt later is best done below the initial crystal growth. The new material moves up by capillary action and evaporation causes additional formations of crystals. No chemical reaction is involved, just dissolving and recrystallization.