Silica Gel - The Basics

We've all seen them, little white packets that say "Do Not Eat" in many of the things we buy - electronics, dried foods, leather goods, etc. What are they? What purpose do they serve? They are packets of Silica Gel, which is a desiccant, or drying agent. They get packaged with products that would spoil or be harmed if they came in contact with moisture. Packaged with dried food products, like jerky, it inhibits the growth of mold. Packaged with electronics, it prevents damage due to moisture. These are only two examples of the multitude of uses for Silica Gel.

How can such a small packet be effective protection against moisture, which is everywhere? Silica Gel can absorb 40% of its weight in moisture, significantly reducing the moisture level in a closed container. Silica Gel is also reusable, not that many of us save the packets from the box of our last pair of leather shoes. Heating the Silica Gel removes the moisture and the Silica Gel is ready to absorb more.

Silica Gel when packaged in a cotton or Tyvek packet meets FDA requirements to be used in packaging with dry food products, but it itself is not food and should not be ingested. Silica Gel has the highest capacity for moisture absorption than any other commercial desiccants. It has millions of pores that absorb and lock in moisture. Despite its name, Silica Gel is a solid. It does not have the wet, slick consistency of things like hair or shaving gels. Silica Gel beads remain a solid and dry to the touch even when fully saturated.

Most Silica Gel is harmless - Silica Gel made with Cobalt Chloride, however, is not harmless. Cobalt Chloride is added to some Silica Gel as an indicator to show when the Silica Gel is at capacity. Indicating Silica Gel beads that contain Cobalt Chloride are blue in color when they are active (dry). As it absorbs moisture it changes from blue to purple to pink when it is fully saturated. Cobalt Chloride is an irritant to skin, eyes, and respiratory tracts. Frequent exposure to Cobalt Chloride can affect the heart, kidneys, lungs, and thyroid. Studies have shown that Cobalt Chloride is a possible carcinogen and is harmful to the environment if not disposed of properly. As a result, its use has been banned in the United Kingdom. Responsible companies in the United States have discontinued the use of Cobalt Chloride in their Indicating Silica Gel. This reformulated Indicating Silica Gel, that does not contain Cobalt Chloride, starts out Orange when dry and turns Dark Green when fully absorbed.

Silica Gel doesn't just come in small white packets. There are many different uses and Silica Gel is sold in several different ways. One of the original uses of Silica Gel was in gas masks in World War I. In World War II it was used to preserve penicillin during transportation as well as protecting military equipment from moisture damage. Today it serves a wide variety of purposes, from protecting electronics prior to purchase to drying flowers, from archival humidity control to protecting cameras in waterproof cases from condensation.