Silica Gel is a porous form of silicon dioxide processed into either a beaded or granular form and commonly used as a desiccant to absorb moisture, water vapor and control relative humidity. Silica Gel is actually hard and much more solid than the name implies and can absorb approximately 40% of its weight in moisture. Silica gel is non-toxic and often used in food products.
Most people have encountered Silica gel packaged in little pouches found in shoe boxes, purses, coat pockets, electronics, vitamins, medications etc. with the familiar “Do Not Eat” printed on them, and are being used by the manufacturer or packager as a packaged desiccant. When used as a desiccant, Silica gel is most commonly packaged in a pouch made of Tyvek, Kraft Paper or Cloth, although it is also widely used in bulk for many applications. These packaged Silica gel pouches or sachets are used to absorb moisture, control humidity and prevent condensation from forming to aid in the prevention of mold, mildew, rust, or corrosion. Also, when used with a food product, they can delay spoilage and extend the product’s useful shelf-life.
Packaged desiccants using Silica gel are offered in a wide variety of sizes and are commonly known as Unit Paks, Pillow Paks or Continuous Strip Paks on a roll or spool. Strip Paks are usually preferred by large volume users with an automated packaging process and auto-dispenser equipment.
There are two types of Silica Gel; regular Silica gel and Indicating Silica Gel. Standard Silica gel is clear to white in color. Indicating Silica Gel has a chemical added to it to give it color, most commonly blue, but other colors are available. When Indicating Silica gel is blue, cobalt chloride has been added to regular Silica Gel, which gives it a bright blue color. As the Indicating Silica Gel becomes saturated from absorbing moisture, it changes color from blue to light pink, almost clear, giving “visual indication” it should be replaced or regenerated. Regardless of whether regular Silica gel or Indicating Silica gel is used for an application, the absorption properties remain the same.