I've a friend who recently built a gun vault in his basement. He's been running a dehumidifier in it set at full tilt since. The discussion came up yesterday as to what humidity level is best for long term storage of guns, bayonets, etc. My thought being that one can get things too dry and damage stocks. What is the general consensus on appropriate humidity level for this type of thing?
Thanks,
Jim

I believe normally dry stock wood is about 12% moisture content so possibly that would be a good benchmark. Some one of the wood merchants will be able to clarify that I am sure. However, in Arizona where the gunstock and other wood get dried to less than 10% it doesn't seem to create any problems. Structural wood in houses gets to about 7% here and does cause shrinkage so somewhere near 12% would seem appropriate.

Wood % moisture and relative humidity are two differing things. As I recall, iron in open air stops rusting at relative humidity below 20%. I can't remember what average relative humidity will stabalize wood at 12% moisture, but am thinking it is above 50%. I think you can over dry wood and risk cracking it and unseating bedding. The biggest risk comes from rather sudden, big and prolonged changes in relative humidity. A gun used mostly in AZ, for example, might be stored at lower RH than one used mostly in FL.

The only way to know relative humidity is to get a hydrometer.
I've had guns in my safe for close to 2 years and have not had a problem using nothing. This spring I bought a 18" Goldenrod heater, forgot the watts but think it is 1500. Put a hunmidity and temperature gage in there and the humidity during 90 degree temperature days was 51% and the temperature inside was 68 degrees F. The safe is in the basement, where the temperature doesn't get above 73 deg. F in summer when it is 90+ degrees outside, and below 52 deg.F when the temperature is 20 deg. outside. That is for Pennsylvania.

I stand corrected about the wattage, it is 18 watts and the temperature rating is 150 deg. F.

In wood working here, measuring moisture using my Mini Lingomat meter, the wood when stabilized in the environment it is being used at, in house, is between 6-8%.

The ideal conditions would be to keep humidity level around 50 - 55% at 68° F ± 2°, coupled with good air circulation and regular monitoring and inspections. Try to keep the temperature and humidity fluctuations to a minimum.

As JDW wrote "The only way to know relative humidity is to get a hygrometer."

I also keep my safe in the basement, temp hovers around 55˚ in winter and 70˚ in summer. I have a basement dehumidifier set for 45% and a golden rod in the safe that keeps the interior temp steady and the humidity at 42%-43%, seems to be working well so far (9 months).

Not trying to step on any toes but I believe it would be a "Hygrometer" you guys are refering to to measure humidity levels.

Cheers
Marcus

You won't have a problem storing cleaned and oiled guns at around 50-55% humidity. A mistake folks make with basements is opening windows or otherwise ventilating them in the summer when outside temperature and humidity is very high. Allowing that hot moist air into a cool basement will cause the moisture to condense on cool surfaces like your guns. I learned this the second summer after I built my house with poured concrete basement walls. I thought a spring opened up because my walls were getting visibly damp near the bottoms and corners. It took a while to figure out but after closing the windows, it became dry as a popcorn fart. A Goldenrod is actually very low wattage. I think the 18" model is only 15 watts. Inside a safe, it will raise the temperature a few degreees and prevent condensation from forming. If your friends' vault is larger than the average safe, a little more wattage will be needed. but it will still be cheaper than running a dehumidifier at full tilt.

The vault is approximately 12' x 16'. The humidifier drains to an outside source and does create some heat. I was in there the other day with a commercial model temp/hum. sensing device and it was 77 deg. with a relative humidity of 28%. To my mind, I thought this might be a bit dry for the wood. The metal is no problem as he keeps things oiled. I also wondered about leather items such as scabbards for his swords, etc.

That sounds too dry for wood and especially for leather.

I agree. I recall reading that humidity much below 40% could cause cracking and permanent damage to the soundboard of my wife's baby grand piano. I can't imagine it is good to dehydrate gun wood and then take it out hunting in all kinds of weather. It would probably be best if your friend dropped the temp and raised the humidity gradually.

I have wondered if anyone makes a very small dehumidifier that would be suitable for 100-200 sq. ft.

Yes, and neither will you have a problem getting finishes to cure.