When storing paper, the following precautions should always be followed:
Do not store paper where it will be exposed to direct sunlight.
Avoid storing paper in humid areas (humidity: 70% or less).
Store all your thick paper in the same environment - a room where the temperature is 20–25°C (68–77°F) and the humidity is 30–65%.
Store on a flat surface.
Do not store paper vertically.
Once opened, store paper in plastic bags.