Jimmy: The difference between leather and gun metal is that leather is organic and will absorb moisture from the air until the moisture content of the leather stabilizes and matches the moisture content of the air, and if the humidity is high, the leather will have enough moisture in it to cause mold growth. That's why the standard advice is to never store any gun in a leather holster or a leather case. Moisture will not condense on a metal surface if the metal surface is even slightly warmer than the surrounding air. That's why GoldenRods work so well. They can keep the metal just warm enough so that no moisture condenses on the metal surfaces. Re your comment that "warm air can be damp, too." Absolutely correct. Warm air can hold more moisture than can cold air (thus, the concept of relative humidity) and that's why your skin dries out in the winter (cold air is drier). As Greg pointed out, the GoldenRod does not reduce the humidity, but it does warm the metal slightly as it warms the air in the safe, thus reducing the RELATIVE humidity inside the safe and preventing condensation. The metal offers a lot of thermal mass, and that's why wide swings in temps (and thus relative humidity) may cause condensation. If the garage warms up quickly, the metal may still be cold for awhile, and that can cause some condensation. Oil is good. Use oil.
