Desiccants for Dry Storage

Keep packaged goods dry and fresh by protecting them from spoilage with desiccants. These shipping supplies adsorb water and prevent moisture from damaging items during storage and transportation. They’re also useful for keeping goods dry when shipping in very humid weather or to damp locations. Manufacturers commonly include packs of these drying agents when shipping foods, pharmaceuticals, and electronics. Browse the varied selection of shipping, packing, and mailing supplies at Staples to find different types of desiccant packs.

Choose the right desiccant for your package
Silica gel is the most common type of drying agent used for keeping packaged consumer goods dry. Also known as silicon dioxide, it can absorb up to 40 percent of its weight in moisture and works best at room temperature. Silica gel absorbs moisture without swelling and is possible to use in tightly packed goods. Some grades of silica gel are safe to include in food and drug packaging. Montmorillonite clay is another commonly used, naturally occurring, and inexpensive adsorbent. While silica gel is the go-to option for consumer goods, clay is the more popular desiccant for industrial goods.

Clay is an excellent moisture adsorbent at low and room temperatures but not at high temperatures. This feature makes it less suitable for preserving items stored and shipped in hot climates. On the other hand, it means that clay recharges easily upon heating. Clay doesn’t swell as it removes moisture from the air. Quicklime, or calcium oxide, is another popular adsorbent. It can retain up to 28 percent of its weight in moisture but removes moisture much slower than clay and silica gel. It does expand as it absorbs moisture and is most efficient at very low relative humidity.

Consider desiccant package size and material
Absorbent agents used in packaged goods usually come in packages of different sizes. The size and number of packets to include depend on the overall size of the shipping box. When shipping individually wrapped items in the same box, it’s best to include a packet in each package. For small boxes, look for the smallest silica gel and clay packages. Larger desiccant packages are ideal for boxes that contain multiple items.

The most common materials used for desiccant packets and bags are Kraft and Tyvek. Known as cover stock, these packaging materials keep adsorbent agents separate from shipped items. They must also permit the absorption of moisture. Kraft paper is an inexpensive cover stock commonly used for clay desiccant. Tyvek is made of a stronger material that handles dust and moisture better. This paper-like material is mold- and mildew-resistant and ideal for storing adsorbents used in high-humidity environments.  

Are all desiccants chemically inert?
No. Some of them are quite toxic. Silica gel is mostly safe. It’s nontoxic, nonreactive, and insoluble in water. Calcium oxide, on the other hand, is caustic and users must avoid inhaling it or getting it on their skin and in their eyes.

What is the difference between silica gel and indicating silica gel?
Indicating silica gel is regular silica gel coated with cobalt chloride. The cobalt salt gives the gel a distinctive blue color that slowly changes to pink as it becomes saturated with moisture. An indicating silica gel shows at a glance whether the adsorbent is fresh or spent. It’s useful for shipping moisture-sensitive electronics and optical instruments.

Can you reuse desiccant packs?
The adsorbent packets included with shipped goods are unlikely to be fresh on arrival. They may not be effective at preventing moisture damage if reused.