A simple home-made in-case dehumidifier

[ridethewind]

This is one of the most enlightening and informative, practical threads I've read. I'm grateful to all of you for such good suggestions. I have the Planet Waves system and here in North Carolina the 2-way system works well. When we get to Brisbane Australia, though, the silicon gel packs will be a lot more useful. Thank you all!


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[N+1]

I thought it might be helpful to have an update, a few weeks further down the line.

What I'm finding, now that my guitars have definitely reached an equilibrium state in their cases as far as humidity is concerned, is that the system (described in detail above) requires hardly any maintenance. Obviously this is primarily because the cases are doing an excellent job of isolating the environment inside them. But I'd expected to have to change the silica gel packs quite often, and although that was necessary at the outset, when the guitars were relatively 'wet', it no longer is. (I should add that one precaution I always take when I take a guitar out of its case to play it, is to close the empty case with the gel packs inside it, to minimise exchange between inside the case and outside.)

Maintenance now consists of checking the hygrometer reading inside the cases every few days - I suspect that once a week is enough, actually. If the relative humidity in a case rises above 50%, I change the gel packs and pop the old ones into a polythene bag. When I've accumulated enough 'wet' gel packs, I heat them in the oven for 90 minutes at 120 degrees centigrade, and that sets me up again for quite a long time.

The upshot is that whereas I expected to have to set up a regular and frequent system of maintenenance, in fact I'm finding there's hardly anything to do to the guitars except play them!

[BOOSE]

Hi N+1, I too am in England only in the NE so opposite to you, we have a lot less rain than you because the Pennines keep it at bay!

I too was going to try the gel packs by all the different companies out there but discovered on reading reviews that a lot of people found that the hydrometer didn't change when putting these things in the guitar with the hydrometer in a case.

My hydrometer reads about 65% ish most of the time and my guitars are always in cases when not being played so to be honest i don't use anything, i'm not saying they don't work but in your first paragraph you stated your guitar was on a wall for 6 months! I'd be inclined to think that's where your problem came from rather that the wet conditions out side.

[Gmountain]

These things work great too.
http://drytopproducts.com/contact-us-prevent-moisture/

[FLRon]

Where does everyone get their gel packs?

[Gmountain]

Originally Posted by FLRon

Where does everyone get their gel packs?

I like Dry Top, but another place is your veterinarian. They get tons of them in medicines and stuff, and are always looking for ways to get rid of them.

You can also buy silica gel on Amazon, florist shops, and hobby stores, like Michaels. They are used for drying flowers.

[musicman1951]

Nice. Thanks for posting.

My luthier, Steve Kovacik, told me to get a plastic soap holder, drill a bunch of holes in it and cut a sponge to fit. Seems to work well. We both use a rubber band around the container.

[FLRon]

Originally Posted by Gmountain

I like Dry Top, but another place is your veterinarian. They get tons of them in medicines and stuff, and are always looking for ways to get rid of them.

You can also buy silica gel on Amazon, florist shops, and hobby stores, like Michaels. They are used for drying flowers.

Thanks, I wouldn't have thought of a florist but it makes sense.

[N+1]

Originally Posted by BOOSE

I too was going to try the gel packs by all the different companies out there but discovered on reading reviews that a lot of people found that the hydrometer didn't change when putting these things in the guitar with the hydrometer in a case.

I don't understand this - in fact I don't believe it. If I put 2 or 3 gel packs in my hessian contraption, it has a very clear, measurable, and significant effect on the relative humidity inside the case. Typically I change the packs when the RH rises just over 50%. The following day, after the change, the RH will have dropped back well down into the lower 40s, and then over the following days, it very slowly rises until replacement time comes round again.

My hydrometer reads about 65% ish most of the time and my guitars are always in cases when not being played so to be honest i don't use anything

Have you measured the relative humidity inside your cases? The relative humidity in the room is no guide to the value of the RH in the cases. My cases are all nicely dehumidified now, but at the start of this experiment they certainly weren't, and the RH inside them (that is, with no gel packs) was well above 60%.

in your first paragraph you stated your guitar was on a wall for 6 months! I'd be inclined to think that's where your problem came from rather that the wet conditions out side.

I'm not talking about the humidity outside (what would be the point?), but about the relative humidity inside the room where the guitars are kept. And yes, of course the problem arose because I'd hung the guitar on a wall in a room where (unbeknownst to me) the humidity was high (70-80%). That's precisely why I carried out the experiments described in this thread, and why it was essential for me to find a solution. But for sure, just putting the guitars in cases without a dessicant would not solve my problem.

[N+1]

Originally Posted by FLRon

Where does everyone get their gel packs?

I bought several packs of them from an Amazon seller - I buy the re-usable type that can be dried out in an oven.

Bear in mind that a 10g pack can only absorb 3 or 4 grams of water, and then it stops absorbing - so they do need to be changed regularly.

[N+1]

Originally Posted by BOOSE

I ... discovered on reading reviews that a lot of people found that the hydrometer didn't change when putting these things in the guitar with the hydrometer in a case.

I've been trying further to think how this could possibly happen (because on the face of it, it doesn't make sense), and I think I have an answer.

Suppose you have a 'wet' guitar. You put it in its case (which is also 'wet') with a couple of 10g silica gel packs and wait. Based on my own experience, I'd expect that after a couple of days the packs will have absorbed almost all the water they're capable of holding: 5 or 6 grams, perhaps. So they won't absorb significantly more water after that, and even if the relative humidity dropped a bit during those two days, it won't fall any further. If you don't have any idea of how much water has to be shifted, you may conclude that the system isn't working.

But the point is, those few grams of water are peanuts compared to the total amount of water that has to be removed (from the guitar AND the case) before the in-case humidity gets down to the ballpark 45-50%. If you don't change the gel packs frequently, you may think nothing has happened, because the packs will become saturated very quickly. I think that's the likely explanation of the reports you've read.

Of course once the RH has fallen below 50% and has become stable, things get much easier to cope with (as I've described above). But for the first few weeks, starting with a 'wet' guitar and case, the gel packs have to be changed very frequently, because we have to get rid of at least 40 or 50 grams of water overall, to achieve the goal.

[N+1]

Originally Posted by BOOSE

I ... discovered on reading reviews that a lot of people found that the hydrometer didn't change when putting these things in the guitar with the hydrometer in a case.

I have more to add, as a result of a conversation I had yesterday with someone who had a high humidity problem. He kept his guitar in a case, but still the humidity was high. I asked if he'd tried using silica gel packs. He said he had, but they made no difference. I asked how much he'd used. He said two 10g packs, and they soon became saturated, and the humidity was still high, so he gave up.

So at the risk of repeating myself, I feel I should spell this out very carefully:

At the start, when the guitar is 'wet', it's necessary to keep changing the silica gel packs frequently. Start with four 10 gram packs. Check them every day, and replace them once their mass has increased to 12 or 13 grams. Check the hygrometer reading every day. If it falls below 40%, take out one or two packs temporarily, because we don't want the change to occur too rapidly. The aim is to get the inside of the case (including the guitar) down to a stable equilibrium, where the relative humidiy has fallen steadily to below 50% and stays there. It will probably take several weeks to achieve that.

Once you reach that steady state, you can ease right off, check the humidity and change the packs once a week or so. But initially, frequent changing of packs and checking of hygrometer is essential.

[bitraker]

I stick two gel packs in an old sock and drop it in the tool case - works like a charm - the in-case hygrometer reads between 45 and 55 even in the driest winter months -

I've never been comfortable hanging water balloons off my strings but nice work...

[Turbogrooves]

Great thread, thanks for posting. Most guitar humidity issues are geared toward humidifying and not 'de'. I live in the Southeast/USA and may be moving to an even more humid environment before long, so I'll keep this info handy.

[N+1]

I realised, to my horror, that when Photobucket banished hotlinking, my carefully mapped out description of my dehumidifier system (see first post in this thread) was virtually demolished at a stroke, because it's not really possible to explain it properly without the photos.

So ... I've uploaded the same set of images to Flickr and replaced all the links in the original post. I think this is now working properly again. At least, it works for me.

Incidentally, now that I've got used to its foibles, the system is working very smoothly. I've found the best combination is to use four 10g silica bags per guitar. A day or two after putting new ones in, the RH drops to about 45%. About two weeks later it's usually risen to just over 50%. I change the bags before it rises to 55%. What that effectively means is that the only activity of any note is to change the bags (which takes maybe ten minutes?) every month or so. Every two months I roast my stock of used gel packs for 90 mins at 120 degrees, and away we go again.

Who needs to play guitars when it's so much fun dehumidifying them?