I bought and am testing some new gel humidifiers, and because so far I think they are excellent I thought I'd mention it here just in time for the holidays. I have no interest, financial or otherwise in the product.
[URL=Arion]Arion[/URL]

It was developed for the open pocket of a violin case, and fits under the headstock in a guitar case. I modified one to fit under the headstock in my mandolin case, and I use a cotton rag as a buffer between the back of the headstock and the plastic.


The thing about humidifiers is that you want them to give out as much moisture as necessary to protect the instrument, but most of them are dumb, and can over-humidify. The gel in this one seems to have a baseline humidity, so that it doesn'’t give out too much too quickly. It also regulates moisture in both directions: in other words the gel will take up extra moisture if that is present.

The claim is that it holds moisture for 1-3 months: I've had one in each of my cases for a month and haven't had to refill, and I am getting 50-55% relative humidity readings inside the cases vs. 40% r.h. in the room. If the r.h. in the room gets much lower I may have to use two in each case. $20 plus shipping from the manufacturer, and there's a quantity discount.

The plastic is microscopically porous, and unless it gets really squashed I don't see how it could leak.

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The Planet Waves is great but the cost of the replacement packs can add up. My guitars are in a wood cabinet and I'm trying something called Heartfelt Beads (found 'em in a cigar forum). They're supposed to maintain a constant level & never need replacing. So far, they're working well. They're probably comparable to the Planet Waves in initial cost.

There are active systems for wood cabinets but I didn't want to be running something while I wasn't home.

What is the RH of those Heartfelt Beads you are using? From their website it looks like the lowest is 60% RH. I think that would be a little too high for a guitar.

He can special-order 50% beads.

www.heartfeltindustries.com
There are all sorts of products aimed at cigar enthusiasts. They offer the beads in mesh bags. I've got mine in shallow plastic trays. I've left them uncovered and sitting in the bottom of my wood guitar cabinet. But I'm going to have to rig up a cover (probably just drill holes in the plastic lid) because the cats keep getting into them.

It cost a bit to get enough beads for the cabinet (as opposed to a guitar case) but, since they don't need to be replaced, I think it'll cost less than the Planet Waves in the long run.