Most types of mold growth in moist clay can increase plasticity because it augments the binding action and attraction of clay platelets. Enhancing the film of water between clay platelets with mold will increase the clay-to-clay attraction.
One recipe to encourage mold growth in clay starts by mixing a 100- pound (45.4-kg) batch of clay formula. Add 1/2 cup (118 ml) of beer, coffee, or apple cider vinegar, or 3 ounces (85 g) of yeast to start mold growth in the clay/water mixture.
Depending on the pH level of the clay-mixing water, the individual clay’s organic matter, and the studio temperature conditions, mold can grow on the surface of moist clay. Most types of mold are beneficial increasing the plastic properties of the clay. Simply wedging the clay will evenly disperse the mold.
However, if you keep moist clay long enough in a warm, dark place, it will grow mold without any additional organic materials being added to the mix.