Indicating Silica Gel

Silica gel is a granular, porous form of silicon dioxide made synthetically from sodium silicate. It’s a naturally occurring mineral that is processed in a granular form or into beads. As a desiccant, it removes water vapor by ADSORPTION onto its surface rather than ABSORBTION into its structure.

Most silica gels come in a paper packet, ready to be applied to packaging structures to avoid degradation of goods by controlling humidity. Use of silica gel became widespread during World War I, with gas mask canisters utilizing silica gels to adsorb various vapors.

Indicating silica gels are joined with a moisture indicator that changes color when the gel goes from anhydrous (dry) to hydrated and saturated (wet). Common indicators used with silica gels are cobalt chloride and methyl violet. Cobalt chloride is the most popular, changing from deep blue to when dry to pink when wet. Methyl violet is considered safer but is relatively new, changing from orange to green, or orange to colorless.

Silica gel is generally recognized as safe when use with food products, and can be renewed by heating it to 250 degrees Fahrenheit for 1 to 2 hours.