Airtight, Dry, & Cool: The best way to store any remaining powder is to place all in an airtight baggie (Ziplock or similar). Remove any remaining air and then keep from light. Store in a cool dry place. Don't store in bathroom—may get too humid and warm. Note: if already mixed with water, then it will not store. Zero added preservatives: the natural plant-based pigments will lose potency & have unpredictable results. Must be used up or thrown out.