This inert substance is an effective means of reducing the humidity in the air surrounding sensitive artifacts. Silica gel will absorb up to 40% of its own weight in water. Five grams of silica will treat approximately one cubic foot of display area. We are pleased to offer a new orange version of traditional blue silica gel. This material has been impregnated with an inorganic iron (< 5%) compound enabling the crystals to change from yellow in the activated, dry condition to orange when saturated with water. Please note: We carry this yellow/ orange self-indicating silica gel in lieu of the common blue silica gel, which contains cobalt chloride and has been declared a possible carcinogen by the EU. Users of the traditional blue version are strongly cautioned regarding its possible carcinogenic effects. Sold by the pound.