Silica Gel: Passive Control of Relative Humidity – Technical Bulletin 33
Source: Canadian Conservation Institute – CCI
Authors: Jean Tétreault and Paul Bégin
The purpose of this Technical Bulletin is to explain the need to control the relative humidity (RH) in a museum environment. Fluctuating RH can damage organic materials, while other objects, such as those made of metal, require a low RH set point to ensure optimal preservation. Controlling RH can be done in a passive way by using a moisture sorbent, the most common type being silica gel, in an enclosure, such as a display case. This bulletin provides an equation, based on assessments of the buffering capacity of common commercial products, to help determine the quantity of sorbent required. It also includes examples of how the equation can be used in various scenarios and proposes methods for conditioning moisture sorbents.