Activated Montmorillonite: Natural, Stable, Inert
Clay desiccant is made from naturally occurring montmorillonite (a bentonite clay) that is thermally activated to open up its internal pore structure, giving a specific surface area of more than 200 m²/g. It adsorbs water vapour physically onto that surface, like silica gel, but it brings three advantages that matter in industrial packaging: it is the most economical desiccant per unit, it is chemically inert and nitrite-free, and it stays solid when saturated, with no liquefaction, swelling or dust. It holds roughly 25% of its weight at moderate humidity, rising with RH, and it performs across a wide temperature range from about –40°C to +70°C.
That inertness is the decisive property. Many cheaper desiccants use nitrogen-based anti-caking additives; sealed inside a moisture barrier bag, those nitrites can drive electrochemical corrosion on copper and bare metal. Clay carries none. It is the reason activated clay, not silica gel, is the desiccant written into military and electronics packaging specifications for direct contact with sensitive components.