What is the optimal humidity level?

Jim is correct. You can only do so much with fire safes.

 

Log in or Sign up to hide this ad.

I have heard that the cement in fire safes can release moisture. The safe I have is actually designed to be a gun safe, where humidity is also not desired. The safe is designed to accomodate an electric "dehumidifier" but all it does is heat the inside of the safe. It might be OK for guns, but I didn't think it was a good idea to store coins in a heated compartment.

It would seem that the solution is to have individual air-tight containers, each with its own silica gel device. I don't know what the ideal container is. Zip lock bags are not air-tight as indicated by the indicator on a silica gel container changing. The plastic storage boxes (e.g. Rubbermaid) sold in department stores aren't even close to air tight. I suppose Tupperware might be, but it's very expensive and I don't think it comes in the right sizes or shapes for coin items.

What do you guys do; at least the ones who don't live in the desert?

 

The problem with any safe is every time you open it, all the air and humidity in the area goes in.
Where I live the humidity is excessively high. I sometimes feel it's about 1,000% if that was possible. I get a kick out of those silly weather people when they say it's raining and the humidity is 68%.
Due to age and several illnesses I've kept my doors and windows closed almost all the time. In my basement some years ago I noticed the humidity was about 45% to 55% almost all the time. I purchased numerous gel packs for dehumidifying and at best 15 of them got the humidity down to about 40%at best and slowly that too just went back up. I purchased an electric dehumidifier with a hose to to basement drain. After two days of that thing running the humidity dropped down to 20%. After that it goes on and off pending the amount of outside air that seaps in as most air does. Usually the humidity in my basement is now about 15%.
Those Silica Gel packs and other such things are for enclosed storage places only. They must be maintained and/or constantly replaced.
If you want to keep your area free of humidity, purchase the electrical ones.

 

EvaDry units can be handled with bare hands during and immediately after recharging. They are UL rated. No worries. No safety hazard. I do 'em all the time.

 

Yep.

EvaDry makes both types - compressor style with a reservoir for condensate (which stay plugged in all the time) and silica gel (which are only plugged in for occasional recharging). The latter are the sort to put in one's safe.

From EvaDry's website :

"When the Eva-Dry is “full” you renew the silica inside by plugging the unit into any power outlet. Heat gently releases water vapor in a few hours."

One doesn't leave these plugged in all the time - only when the indicator shows they need recharging. They work fine for me. I use the small ones; they make bigger ones for larger spaces (small closets, etc).

 

I've never known EvaDry to require more than 6 hours. Plug 'em in before leaving for work or before hitting the pillow. Painless. No need to fire up the oven, so it needs much less energy.

 

Polyethylene bags are permeable. I don't know of any safe air tight bags. For boxes, there are some made of aluminum, stainless steel, or plastic that are probably fine. They'd typically have a an o-ring to make the box waterproof. The most cost-effective boxes I'd look at are made for ammo or kayaking (e.g. Otterbox or Pelican). I do not know for certain what plastics they use but I think those would be worth checking out. The waterproof bags I've seen are almost always PVC so it's not even worth asking how airtight they are.

 

The ones I have measure 3X5" and actually have recharging instructions printed on them. They say to heat them up to 245 degrees for 16 hours. That's a pain in the neck. And they DO fall apart afterwards.

I checked on the big (750 gm) metal canisters of silica gel and they say they can be recharged in 3 hours in the oven. I think I'll pick up a couple of those.

 

Here's a picture of one. They are sold at JP's Corner, and probably other places. They charge about $29 for 60 of them. This one has different instructions for regenerating than mine. I guess that shows what an exact science it is.