Nova Color Artists' Acrylic Paint dries by evaporation so it is important to keep jars capped. Lids and jar threads should be kept free of paint to insure a tight seal. A few drops of purified water can be added to the paint surface before closing. Tap water, soiled brushes and stirrers, or reused food jars can introduce bacteria into the paint and cause mold. Clean brushes, tools and storage jars regularly with alcohol, bleach or other disinfectant. Store paint at 40-85 degrees F.