This is a re-post about the type of damp box I came up with in a pinch. Actually, I now use boxes about 8 x 8 x 48 for the longer barrels and they work great. They are $3.50 and I throw them away when I'm done so I don't have to store the damp box. All the other parts go back on the shelf.
I recently had to refurbish a pile of parts that used to be a Pacific model Ballard rifle. It was found in a California mountain meadow 40 years ago with no butt stock and many damaged internal parts.
To get the rifle back in shooting condition, I first had the barrel relined by Wyoming Armory . Then I repaired the internals and made new stock parts. I wanted to refinish the metal work without overdoing it, so I decided that I would not do much more than clean the metal parts and brown them. Since the humidity around Southern California is usually not very high, I wanted to use a damp box and considered building a wooden one. However, storing it afterward would have been an issue. So I made up the following disposable damp box from a discarded cardboard box.
**(modern content edited to conform with ALR rules**
The box was big enough to brown the barrel and, of course, all the remaining smaller parts. Inside the box I placed a GE Hot Pot to heat water, a surplus muffin fan to circulate the moist air, a light bulb for heat, and a hygrometer to keep track of both temperature and humidity. The light bulb was also on a dimmer to control temperature a little better and keep the inside of the box from reaching the dew point where water would condense on the parts and ruin the finish.
It took a day and a half to get the metal finished in the damp box.
I threw the box away when I was finished and now I don't have to store it anywhere in a small shop. I'll need a longer box for the next rifle that is in work.