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Problems with humidity - advice needed http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=20453	Page 1 of 1

Author:	Matthew Jenkins [ Mon Jan 12, 2009 9:27 am ]
Post subject:	Problems with humidity - advice needed
Well things are just going from bad to worse for me. I had a disater recently which I posted and on the back of that I ran a straight edge over some bodies I am currently building. Low and behold, yet another problem The backs are badly sunken so the humidity is obviously all wrong. I have never tested for humidity (there's so many things to learn I'm not keeping up at all!!). Reading the archives It seems I should have learnt about RH before I even started building. I will buy a humidifier and a gauge and keep it right from now on BUT......... ....... 1) Are my bodies going to be ok? I don't want to lose them. They are well made and ready for binding. There are no cracks or anything, just a bad dip in the backs. 2) Will a bucket of water in the workshop help the humidity untill I can get sorted with the correct gear?? I want to continue building but it seems that I'm scared to do anything now for fear of disaster later on. Thanks in advance for your replies. I'm beginning to feel really dumb now. All I ever do is post about the problems I'm having but I'm just glad I can rely on your help and advice. Thanks Mat

Author:	Laurent Brondel [ Mon Jan 12, 2009 9:55 am ]
Post subject:	Re: Problems with humidity - advice needed
It sounds like you braced the back and assembled the body at a much higher RH than what it is now in your shop. This can happen also if your wood was not properly seasoned or acclimated long enough to your environment before building. There are plenty of threads concerning RH control in the archives, have a look. Generally you want to build at a fairly constant RH between 40% and 50% RH so your guitar can move either way without damage. What kind of guitar is it and what tonewoods did you use? How's the top? Regardless you should stop here, buy a hygrometer and humidifier to control the RH where you build, and monitor the guitar for a week or so before making any decision. Worst case scenario, you'll have to take the back off, possibly re-brace it and move on.

Author:	SteveCourtright [ Mon Jan 12, 2009 10:18 am ]
Post subject:	Re: Problems with humidity - advice needed
Mat A bucket of water probably won't make a measurable difference in RH.

Author:	Matthew Jenkins [ Mon Jan 12, 2009 12:10 pm ]
Post subject:	Re: Problems with humidity - advice needed
Thanks Steve Laurent - the tops seem to be fine. One is an 'OM' - mahog/Engleman, the other is a Grand Aud - Mango/Redwood. All wood was acclimatised and well seasoned. thanks

Author:	Todd Rose [ Mon Jan 12, 2009 12:27 pm ]
Post subject:	Re: Problems with humidity - advice needed
I'm with Laurent. I wouldn't do anything until you've had your boxes sitting in a humidity controlled space, at about 45% RH, for a couple weeks, and see what they look like then. That means you need a hygrometer, a psychrometer to calibrate the hygrometer, and a humidifier (assuming your RH is currently too low). You also need to seal off the room pretty well, and you may also need to add a layer of clear plastic over your windows if you find you're getting a lot of condensation on them, as that can also rob moisture from your air. I just replaced my old Beamis humidifier in my shop with a new Venta-Sonic (got it at Bed Bath and Beyond), and that thing is the cat's pajamas. It maintains the humidity exactly where I want it and requires almost no maintenance other than refilling its tank every 3 or 4 days. I love it. I wouldn't complete the guitars if the plates are still sunken once they've acclimated to a 45% RH space. As Laurent says, you would just have to pull the plates and rebrace them.

Author:	Matthew Jenkins [ Mon Jan 12, 2009 12:32 pm ]
Post subject:	Re: Problems with humidity - advice needed
Thanks Todd Just to add - my Workshop is insulated and double glazed with the temp constantly between 18 and 20 degrees. I will get a hygrometer asap and then I'm assuming it's a humidifier I need.

Author:	Rod True [ Mon Jan 12, 2009 2:06 pm ]
Post subject:	Re: Problems with humidity - advice needed
Yes Mat, Hygrometer first, but you need to make sure it's accurate, that's why Todd suggested the psychrometer in order to calibrate the hygrometer (I know, seems redundant but it's necessary) as hygrometers can either be out or go out of accuracy on regular occurances. That's why most of us who take the RH level seriously have more than one (up to 3) different hygrometer's. I'd also forget about getting a digital one unless you buy something that's made for a humidor or similar. Even then, I'd trust any analog over digital any day of the week. Also, the analog's are usually easier to adjust when needed. After you know where you're RH level is, then you can assess your guitars. Best case is that when you reach 45% on your calibrated hygrometer, the backs have come back to shape (although honestly it takes a long time for this to happen, even with stable humidity control) and you're good to go. Worst case, you may have to take the backs off, remove the braces, re-brace and glue the backs back on the rims. A humidifier is key in controlling low humidity levels and a de-humidifier is key in controlling high humidity levels. And sometimes they can and do work together to make things as stable as possible. Controlling the build environment is really the most important task when being serious about building instruments or anything with wood really. We can have the best building chops but if we don't have control over the atmosphere in which we build, then our instruments become nearly worthless.

Author:	Laurent Brondel [ Mon Jan 12, 2009 2:52 pm ]
Post subject:	Re: Problems with humidity - advice needed
I do not know where you are located in the UK, but northern France is going through a pretty unusual cold spell (-5º to -10ºC), and when the temp drops below freezing the RH tends to drop too, perhaps in the 20% range. So your backs may come back to a nice shape once the RH gets to the usual range. Just an idea.

Author:	Matthew Jenkins [ Mon Jan 12, 2009 2:59 pm ]
Post subject:	Re: Problems with humidity - advice needed
Thanks Rod - I've just ordered two hygro's Laurent - great point. We've had that bad cold snap, got to -6. It's warming up now so I'll see what happens. Thanks y'all

Author:	Dave Higham [ Mon Jan 12, 2009 3:29 pm ]
Post subject:	Re: Problems with humidity - advice needed
I was thinking the same thing as Laurent. I'm in S W France and although we're about the only bit of France without snow, we've had sub-zero teperatures for about a week now. My workshop is heated and insulated and, left alone, the humidity is down to about 32% to 35%. I've been fighting it by intermittently letting an electric kettle boil for a few minutes (it's a very small w/s) but I must get a humidifier.

Author:	Rod True [ Mon Jan 12, 2009 6:14 pm ]
Post subject:	Re: Problems with humidity - advice needed
Dave, I have a 185 sft workshop and I only have a 3 gal humidifier. I got it at a local thrift store for $5 I think. Try that, you don't need to spend much if you only have a small area to control.

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