Hi.
The problem I've found with silica gel bags is that they're won't last long and are rather expensive to use. My photographing friends have to use them constantly and there was a tip on a photog site ages ago. Crystaline cat-litter is the same stuff, You just need to bag it.
What I would do is to find a hermetic storing cabinet or a case. I have water-tight PELI (
http://www.peli.com/ ) travel case that is not long enough for instruments, but I'm sure they have ones for instruments too. WILL cost You an arm and a leg and your left testicle, but that will be the last case you'll ever need to buy

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Iron Maiden uses them so those must be good

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Regards
Sam