What theyare is very small crystals that swell up like 50 times their original size when you add water.I've only used a small sample,they work.there are others that swear by them and you need add only distilled water.Here is some info from one company that sells them.Slim had posted on an earlier thread about them but I can't find it,I only wanted to mention they now have a 65% media to go along with their 70%.................:
Climmax Premier Media is the same tried, tested, and proven technology that is used by museums to protect priceless works of art and one of a kind manuscripts. If it is good enough to protect multi-million dollar works of art, it will protect your cigar investment better than any other humidification medium on the market today. The Climmax Premier Media are sold in 1/4, 1/2, and 1 pound increments and will provide precise humidification control for approximately 5 cubic feet per pound. The media should be stored in a water-tight, open top container and placed inside your humidor. The media are manufactured to maintain 70% humidity with a variance of +/- 2% RH. All you need to add is distilled water.