Is Your Silica Gel Past Its Prime?

Submitted by Michael Tucker

How can you tell when your Silica gel is over the hill?

Everybody knows that Silica gel is great stuff. It can protect almost anything from dampness and moisture. It's a "desiccant," a substance that sucks up water in its environment. In fact, it's one of the best desiccants ever discovered, which is why you're probably already using it to safeguard everything from important documents to firearms.

But, how do you know when the Silica gel you're using is full up? When it has already absorbed as much water as it can and you need to get new packets or loose grains?

That used to be pretty hard to do. But, now, vendors are starting to produce Silica gel that will alert you when it has reached the end of its useful life. It's known as "indicating gel." This means that the gel granules will change color when they're saturated. Usually, they'll start off orange and then go to green when they're full. So, there's no more guessing. You can tell at glance if you need new gel or packets.

However, a quick and important note, not all indicating Silica gel is the same. Some vendors make their gels change color by adding cobalt (II) chloride to the product. Cobalt (II) chloride has been classified by the International Agency for Research on Cancer (IARC) as a Group 2B possible carcinogen. This means that according to well-supported and international research, there is a very good chance it causes cancer.

Fortunately, other vendors shun cobalt (II) chloride., for instance, never ships any silica gel with the chemical in it. Instead, it markets indicating gels that use different substances that provide color changes safely and easily.

One product, for example, is the "Moisture Indicating Silica Gel Packet." This is a Silica gel packet, exactly like any gel packet you'd use, with one additional feature—it has a transparent skin. You can see the grains inside and tell if they've gone green or not.

By like token, the company offers a variety of dehumidifying canisters and boxes that come with their own little windows. You just have to give it a peek to see if the beads are past their prime.

Finally, you can also get boxes of Silica gel with "humidity indicating cards" attached. The cards have a series of dots on them that change color depending on the level of humidity. Again, all you need to do is look to discover whether or not you need a refresh.

As an aside, it is possible to reuse silica gel—though it really isn’t cost effective. However, if you really want to do it, you can take saturated loose Silica gel (stress loose, don't try to reuse packets!) and drive the water out of it. You simply put the gel grains on a cookie sheet, put the sheet into your oven, and heat at 200 degrees Fahrenheit for a couple of hours.

Though, bluntly, it is a lot easier to order up another batch of dry Silica gel. It's cheap, quick, and simple. And you don't run the risk of alienating any cooks in the house. ("You used my oven to do what?")

So, next time you need Silica gel, consider getting an indicating gel. That way, you'll never be in the dark about whether it's working or not. Maybe in the orange, or green, but not in the dark.