Desiccants help to control moisture and prevent damage to a wide array of items during storage and transportation. Their ability to adsorb moisture makes them valuable in a variety of industries, from manufacturing to electronics to food packaging. But how long do desiccants actually last, and what factors can influence their lifespan?
How Do Desiccants Work?
Desiccants work by taking moisture from the air, creating a dry environment that protects sensitive materials from damage caused by humidity. Made from hygroscopic substances (materials that naturally attract and retain water molecules from the air), desiccants control humidity levels and prevent issues like rust, mold, or mildew. These powerful moisture control packs and pouches are ideal for enclosed spaces like product packaging, containers, and totes, where they protect metal parts from corrosion and moisture-related damage.
The way desiccants work depends on the material used. For example, silica gel contains tiny pores that trap moisture through adsorption—a process where water molecules cling to the surface of the desiccant material. While each type of desiccant may vary in how it works, their purpose is the same: to reduce moisture to protect metal parts and other valuable goods from damage. Let’s take a closer look at the different types of desiccants and how they work.
Types of Desiccants
There are several types of desiccants, each capable of controlling moisture in different ways. Common types include:
- Clay Desiccants: Also known as montmorillonite clay, activated clay, or bentonite, clay desiccants are made from natural materials and are among the most economical desiccants. Clay can adsorb up to 30 percent of its weight in water vapor (moisture) before reaching saturation. While clay is effective within a temperature range of 32°F (0°C) up to 120°F (49°C), it performs best at approximately 77°F (25°C). Clay is biodegradable and environmentally friendly, further enhancing its appeal as a moisture control solution.
- Silica Gel: One of the most common desiccants, silica gel is made from tiny beads of silicon dioxide, which adsorb up to 40 percent of its weight in water vapor (moisture). Silica gel is non-toxic, non-flammable and is best suited for use in temperatures up to 120°F (49°C). It performs best in conditions between 70°F and 90°F (21°C to 32°C) with high humidity levels (60-90% relative humidity).
- Calcium Chloride: Actively absorbs and retains a large volume of water vapor (moisture) quickly—up to 200 percent of its weight. Calcium chloride is non-toxic and is effective across a wide temperature range from approximately -4°F (-20°C) to 194°F (90°C). Its effectiveness requires careful monitoring because it can become saturated quickly and may need frequent replacement in high-humidity environments.
- Molecular Sieve: A synthetically produced and engineered desiccant with a highly porous, three-dimensional, crystalline structure, which allows it to remove moisture at a much faster rate than clay or silica gel. It can adsorb up to 21% of its weight in water vapor before reaching saturation, and it offers excellent moisture retention capabilities even at high temperatures of up to 300°F (150°C). Additionally, molecular sieve is highly effective in environments with humidity levels above 40% relative humidity (RH).
How to Make Your Desiccants Last Longer: Storage Tips for Desiccants
Proper storage and handling are key to maximizing the lifespan of desiccants. Secure storage and effective use can significantly extend their performance and moisture-absorbing capacity. If you’re not currently using your desiccants, it’s important to store them in an airtight container to prevent them from absorbing moisture prematurely. While your desiccants are in use, whether during storage or transportation, it’s also important to keep the packaging secure and minimize exposure to open air as much as possible. This helps maintain their effectiveness and ensures they perform at their best for the duration of their intended use.
Here are a few other tips to make your desiccants last longer, both in-storage and in-use.
How Long Do Desiccants Last?
The lifespan of desiccants depends on the type and the environmental conditions they are exposed to. To understand how long desiccants last, we exposed two different types of desiccants, clay and silica, to air in an open container. Eight layers of each type of desiccant were subjected to 80% relative humidity at 25º C for 48 hours. The results of three of these layers are shown in the charts below. From this, we can determine how long different amounts of desiccants last when exposed to open air.
These charts show the weight gain, due to moisture, of each substance over time. Notice that the third, bottommost layer, shows very little weight gain across both substances, while the topmost layer continues to gain moisture over time. The silica continues to retain moisture at a mostly steady rate over time, while the clay pulls in moisture quickly in the first twelve hours, but then its rate of absorption begins to decline.
Each amount of desiccants, when exposed to open air, can be expected to last for:
- 1 gram: 30 minutes
- 1 to 5 grams: 1 hour
- 5 to 20 grams: 2 hours
- Over 20 grams: 3 hours
How Long Do Desiccants Last In Storage?
The above experiment shows how long desiccants can last and how effective they will be over time when exposed to open air. But how long do desiccants last if they’re stored in a sealed container?
This depends on how well the container is sealed and how much moisture is present in the surrounding air. We ship ARMOR desiccants in vacuum-sealed foil and/or poly bags to prevent exposure to the outside air. The typical shelf life for ARMOR desiccant packets is 24 months from the date of manufacture.
Understanding how long desiccants last and how to properly store them will help ensure that they continue to protect your metal parts effectively over time. Monitor your desiccants carefully and look for signs that they may have lost their adsorption or absorption power, such as changes to their size, color, or texture. By ensuring your metal parts are covered and that your storage containers are secure, you can maximize the lifetime of your desiccants.
