Gun Safe Moisture

Buffalo and its suburbs escaped with few power outages after the area received more than 5 feet of snow in November of 2014, but Mother Nature’s wrath usually ends differently. In February of 2013, 650,000 homes and  businesses lost power after a nor’easter, and millions of homes went dark—some for weeks—after 2012’s Hurricane Sandy.

Losing power to your gun safe’s heating unit for an extended period can drench the contents in rust-causing moisture, regardless of perceived airtightness. Aside from opening the door and microscopic leaks, most high-quality units have a small, removable plug at the back to run an electric heating unit (or wire a light bulb) in which humidity invades. The bulb or element creates a slightly higher temperature, which in turn increases the interior air’s ability to hold water molecules in suspension, and maintains mild gunmetal warmth to prevent condensation.

The approach is effective—until the power goes out. An understanding of the dynamic begins with dew point, the temperature at which water vapor begins to condense. Its value increases with relative humidity and once the temperature of the safe’s contents reach that point in their cooling, “dew” collects on their surfaces. But, metals are efficient thermal conductors, so when a receiver at the bottom of the safe cools faster than the muzzle end atop (heat rises), it drains that warmth from its entire length.

Desiccants to avoid gun safe moisture

A different (or better yet for safe owners, concurrent) method of management is to remove humidity from the air by employing a desiccant. The options available to gun owners today are convenient, inexpensive and I put several to the test.

The exam began with an industrial version called Drierite. According to gun-owning company spokesman Joseph Hammond, “Much of it is used for keeping large liquid storage tanks free of moisture…Bio-diesel and ethanol storage are a growing market for us.” It sounds dangerous, but it is manufactured from gypsum—a naturally occurring mineral.

One ounce of No. 4 mesh (a measure of the material’s pebble size) went into a small, airtight container for 72 hours. Relative humidity dropped consistently to 10 percent—a reduction of roughly 40 points—through five cycles of the test. Water vapor locks into the material, so there is no watery mess. It recharges by baking two hours at 450 degrees. Hammond uses 2 pounds of No. 6 mesh in his gun safe, but warns, “I would not recommend sealing up your ’03 Springfield with 10 pounds of Drierite. The metal would never rust, but I’d say the stock would shrink and probably split pretty quickly.”

The Liberty Safe Mini-Canister has 40-grams of silica gel that turns pink when the moisture needs to be baked out. Cobalt chloride locked in the pebbles does that work and the small unit comes in an oven-safe metal canister. Its results were also extremely consistent, although not industrial grade. It dropped relative humidity into the 20s, even after five recharges (300 degrees for 3 hours).

Eva-Dry makes indicating desiccant canisters that are wireless, but simply plug into a wall outlet for renewing (12 to 15 hours). In identical testing, it was every bit as effective as the Mini-Canister, although the results were more methodical. It took nearly two weeks for the humidity to drop to the same level. An indicator window turns pink when it’s time to recharge and cost. The company co-owner regularly tosses a disposable version in his carry gun’s case when traveling to avoid rust.

The final word in our tests comes from Internet-recommended silica gel kitty litter. Despite an airtight package, it was ineffective (saturated) at first. After baking, humidity dropped with 40 grams of the stinky stuff, but it never reached that of other desiccant levels and effectiveness diminished with each recharging. So if you really want to protect your guns, buy a quality product—unless you have an incontinent cat.

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