Silica gel is an amorphous form of silicon dioxide, which is synthetically produced in the form of hard
irregular granules (having the appearance of crystals) or hard irregular beads. A microporous structure
of interlocking cavities gives a very high surface area (800 square meters per gram). It is this structure that
makes silica gel a high capacity desiccant. Water molecules adhere to the gels surface because it exhibits
a lower vapour pressure than the surrounding air. When an equilibrium of equal pressure is reached,
no more adsorption occurs. Thus the higher the humidity of the surrounding air, the greater the amount of
water that is adsorbed before equilibrium is reached. It is in these higher humidity conditions (above 50%
Relative Humidity) that stored or in-transit items are susceptible to damage.