Hey Cloudsweeper.. In my safe I use the silica. It is recharged by placing the bag, not the cardboard box in the oven at 250 degrees F for 2.5 to 3 hrs. Cost is minimal..I spent 9.00 on a box that controls 33 ft squared. It has indicators on the box bottom when it needs to be cooked...go to air tight website and see for your self...www.air-tights.com RickieB
The link works much better when you spell it correctly. I've used rechargeable silica cartridges in my safe for years, without any problems, and without messing up coins or documents with high humidity. I've never used clay because the locksmith who installed my subfloor safe many years ago strongly recommended against it, and in favor of silica.
You beat me to it. I too use dehumifiers. I've been using them for about 20 years now I think. Not sure but for a long, long time. No problems with any coins changing into anything. Also, much healthier for myself, the whole house, the funiture, photo equipment, etc., etc. Silica stuff is a waste of time.