Make sure to store 521 Marine Grade Epxoy at 60-90°F in a dry place. After use, tightly reseal all containers. Epoxy resins that are contaminated with dust or moisture, or are subjected to low temperatures may crystallize. Do not use material that has any sign of crystallization until it has been restored to a natural state. A crystallized resin or hardener can be returned to its original state by heating the material to 140°F to 150°F and stirring until it returns to the liquid state.