I learned a couple things from this thread. Years ago I worked in the woods wearing 10" corked boots and heavy rag wool socks that extended at least 3 inches above the boot top. Saved all the socks for occasional hunting use and started storing mostly revolvers in them. Barrels from 6 to 8 3/8". The socks cover the whole handgun, grips and all. I've been doing this for 40 years in gun safes inside my residence's. Some houses were within one mile of the ocean, one in the mountains and this last one in the valley. I've always heated with wood and don't have much of a humidity problem. Summer or winter. I have never had a problem. Some of the Colt Police Positives and Officer Model Target revolvers are over 60 years old. Some over 70.
Never thought about cotton, never had heavy socks made out of it. My only problem, all hand guns are in the same looking sock. If I want to use a particular weapon I end up looking at about half of them until I find it. So by accident they get checked semi regularly.