Different Types of Desiccant Materials:
- Montmorillonite Clay
- Silica Gel
- Indicating Silica Gel
- Molecular Sieve
- Calcium Oxide ( also known as Quick Lime)
- Calcium Sulfate (CaSO4)
A natural occurring adsorbent that will successfully regenerate for repeated use at very low temperatures without substantial deterioration or swelling. Clay is inexpensive and highly effective within normal temperature and relative humidity ranges.
A form of silica manufactured from sodium silicate and sulfuric acid. Like clay, silica gel is non-hazardous and is capable of adsorbing 40% of its weight in water vapor at 100% humidity. Silica gel has a porous molecular structure that closely resembles a sponge and has the highest capacity of any commercial desiccant for moisture absorption.
Indicating Silica Gel
have similar adsorbing capacities as regular silica gel, it changes color to alert the user that the desiccant is reaching its adsorption capacity.
A manufactured crystalline version of zeolite containing a network of uniform pores and empty cavities. Molecular Sieve is derived from sodium potassium or calcium alumina silicate. It is the most aggressive and expensive of the primary desiccants.
Calcium Oxide is also known as Quick Lime
In comparison to other materials, it will adsorb a much greater amount of water at low relative humidity. It is effective in retaining moisture at high temperatures and it is relatively inexpensive as compared to many other desiccants.
Calcium Sulfate (CaSO4)
It’s an inexpensive alternative available in suitable packaging forms. Calcium sulfate is created by the controlled dehydration of gypsum, acting as a general purpose desiccant, geared mainly toward laboratory use. The low cost of calcium sulfate must be weighed against its equally low absorptive capacity. Sulfate adsorbs only up to 10% of its weight in water vapor.
Although carbon does not absorb moisture, it is commonly packaged for use as an odor remover. Carbon can be blended with desiccants to provide protection against odor and moisture in the same package.
How Are Desiccants Best Utilized?
Desiccants are most effective when used within a rigid sealed container; this allows the desiccant to absorb the moisture vapor trapped inside of the package. Products are best packaged in a manner that does not allow additional water vapor to enter into the enclosed environment. A humidity indicating card (HIC) is often used in conjunction with a desiccant to indicate humidity levels inside a package and when the desiccant needs to be replaced.