Formed from silicon dioxide, silica gel is amorphous and produced synthetically into granules that are hard. In appearance, it looks like irregular crystal like beads. Since their micro-porous makeup has cavities that are interlocking, the gel has an extremely high area of surface, it makes for a perfect desiccant of high capacity.
Because it has a lower vapor pressure than the air that surrounds it, molecules of water can easily adhere to its surface. Absorption is no longer possible when equal pressure is established. Thus, if the humidity is higher in the air, then the greater absorption of water. It is important to note that high humidity, particularly above 50%, can cause damage to the gel that is being transported or stored.
Since silica gel is non-toxic, odorless, and non-corrosive, it provides premium large volume desiccant dryers with lower energy costs. Compared to other desiccants, it has very stable thermal and chemical characteristics. This choice of desiccant is typically white and referred to as non-indicating. Once the gel adsorbs the moisture, it will remain unchanged physically. For gel that is self-indicating, an additive is added to the basic gel so that it change color upon the adsorption of water. A self-indicating silica gel allows for a visual indication of the level of activity that is taking place.
A desiccant dryer is typically used to dry air for various applications. This type of dryer removes water molecules from the surrounding air by way of a desiccant that can absorb it. Although there are manual desiccant dryers, many are regenerative. Dryers have two cylinders that are connected by a valve system and contain a desiccant material like silica gel. When the first cylinder of desiccant is saturated, the air can then be passed to the cylinder that contains dry desiccant.