- Written by Super User
A desiccant is basically a substance that either causes something to become dry or which keeps something in a state of dryness.
The most commonly used form of desiccant sachet is the ubiquitous silica gel sachet which contains many granules of silica gel. The granules have a porous structure and an extremely large surface area relative to their size which enables them to absorb water efficiently. These granules literally attract water on the basis of vapour pressure, drawing it within their structure. Silica gel will not absorb water indefinitely but will stop at a given threshold. For this reason it is necessary to change silica gel sachets according to the conditions under which they are used and to vary the amount used depending on how much moisture a given environment contains.