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First kit; humidity check!
Rick Homan

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I searched "humidity" in the forum here and read lots of interesting stuff. Thanks to all the posters. I do still have a question though. My StewMac 000 mahog/bolt-on kit just arrived, and I am setting up shop in the garage. Relative humidity there has been 64% to 67% for quite a while now; temperature is a steady 66F to 69F. Not much variation there, but a ways off from the ideal 45% to 50% RH. Is it far enough off to bother with the sealed box and silica packs for acclimating and keeping the wood?

As I understand it, the constant humidity would mean I should not have problems while building. But would a guitar built at that humidity be less stable if it went to live in the desert or in a place with really cold winters?

Aug 16, 07 | 7:28 am

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Rick you're right in your perception. If you don't face a low humid period and you cannot control it, then you have to deal with it as it is. My local luthier always builds at 58% because he thinks that the most avarage humidity in Holland. The area the guitar is gonna stay in is of major influence on your decision. I, for me, decided not to work on the plates above 60%. But that is me and my 2ct.
good luck, Herman

Aug 16, 07 | 9:03 am
Ken Cierp

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If a gutar built in an area with average relative humidity of 66% and is taken, played and/or stored in area that only has 45% humidity, you can surely expect severe problems with cracks and all sorts of top and neck distortion in a very short amount of time -- hours!!! Removing 30% of the moisture is a big deal in wood working terms. Because guitar construction involves assembly of parts with the grain running in opposite directions the shrinkage issue is of even greater concern.


Aug 16, 07 | 11:50 am
Rick Homan

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Thank you both for your replies. It is good to benefit by your experience as I begin.

I need a clarification. According to what you say, Ken, Martin guitars which are built at 48% RH in the climate-controlled factory could not survive a winter in Pennsylvania where the RH in people's homes routinely reaches the low-30's% because they would lose a third of their moisture. Obviously, this is not true. Am I missing something here?

Aug 17, 07 | 3:09 am
Ken Cierp

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If those PA folks that have their guitars in a house where the humidty drops into the 30% range and they do no have a "case or sound hole" humidifier, they will have cracks and problems with neck set etc. And I beg to differ with you, it is TRUE. Why do you think those guitar accessories are sold??? Go to the Taylor site and read up on the care and feeding of a guitar. Also you could get a copy of Hoadley's "Understanding Wood" my personal reference text. You certainly can do what you please, all I am pointing out is be prepard to cope with the laws of nature -- they can't be changed. You really answered your own question "Martin Guitars are built in a factory with 48% humidity". If 65% was a good idea that's where they would have the humidity set.


Aug 17, 07 | 3:51 am
Bill Cory

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Rick -- when I worked in a guitar store here in Colorado Springs, about halfway through the winter, we would have people waiting on Monday mornings after cold weekends for the store to open so they could find out what was wrong with their guitars -- mysterious cracks, strings suddenly hitting the 20th fret from a sunken soundhole/bridge area, etc. All symptoms of dry guitars. Usually, they were peole who moved to COlorado from Texas or California, sometimes from the East -- and a cold Colorado winter combined with central heating gave them a problem they'd never encountered. We would humidify them for a couple of weeks, sell 'em an overpriced Planet Waves humidifier, and send 'em home.

It takes varying amounts of time for a guitar to dry out, depending on the ambient RH of its normal environment vs its new environment -- and as the Taylor site says, a guitar can easily hold (and lose) two ounces of water from drying out. Thanks to Taylor, most people know of this. We who build them, though, have to be careful. If you build at 65% in the summer and your guitar ends up living in a 35% environment, (or lower in the winter from heating) it will dry out and possibly crack.

The reason Martin builds at 48% and Taylor at 47% (their figures) is because that is in the middle of the range we usually live with in the temperate climates: between 20% and 70%, and those are extremes. It's normally more like 30% to 60%, and a little soundhole humidifier will take care of the 15% of RH loss easily; and 15% of moisture gain isn't normally enough to damage the guitar. So they build "on the average."

Also, remember that cold air holds more moisture than warm air (think of fog hanging in the air on a cold night), so the same amount of moisture in the air would show as a lower RH at a cold temperature than it would at a warmer temperature, since the "Relative" in "Relative Humidity" is relative to 100% at a given temperature.

Aug 17, 07 | 9:09 am
Rick Homan

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Thank you, Herman, Ken and Bill! It is great to be able to discuss these things with people more experienced than I am. I think I now have a good grasp of the issues involved.

FWIW, I talked to the StewMac tech support guy at the Healdsburg Festival today and he said similarly that if it lives in the climate where it was built, no problem; but if it's built at 65% RH it would be less reliable in very dry places. I ran past him the option discussed here of storing the kit at ideal RH, and taking it out for work, and he was against that. He seemed to think the wood would start to move in only a few hours while working, and that it would be better for it to remain at a constant RH.

Does anyone know how Martin controlled humidity at their old North Street factory back in the "Golden Era" which would have been before air conditioning. I imagine they had a pretty good sense of the building's microclimates -- attic vs. cellar, for instance. I'm just wondering if there are some low-tech solutions which may no longer be obvious to us.

Aug 17, 07 | 5:16 pm

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Rick, clearly there is a lot of wiser brains than mine above but, it appears that you are getting close to the point I reached on humidity. My work shop can not be sealed, therefore I can not control humidity. For me it came down to not building at all or just taking my chances with humidity. I try to work during periods when the RH fluctuation will be minor.

I like you are interested to know the answers to how it is explained that some of the greatest guitars were built way before any of the technologies of today were around and how is it that touring artists go from one extreme to the other in a day without their instruments falling apart in their hands.

Aug 18, 07 | 10:17 pm
Ken Cierp

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I would say that those old instruments are not without problems --- many/most have indeed fallen apart. If artist do use their vintage instruments in concert they are stored in double walled humidified cases -- Actually, I thought most artist had studio instruments and also road instruments?? I think your research will indicate that the assembly operations were done when conditions were best and/or usually in the winter months. Sealed building or not, running a dehumidifier is a very good practice. You are also correct regarding the lack of options if the choice is build or not build, well that is not a choice I'd build and take my chances.


Aug 19, 07 | 9:20 am
Ken Cierp

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"Instruments like humidity, they don't like dry" If guitars simple acclaimate and it does not matter what does that statement mean?? Now I'd say that is confusing??


Aug 20, 07 | 3:06 pm
Bill Cory

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Original posted by Rick Homan above Ted's Aug 19 response ... Sorry it was deleted accidentally.

Rick Wrote:
"I got an email back from a friend who has many years' experience repairing guitars and many years experience as a dealer in "Golden Era" Martin's and Gibsons. I had described my situation at the top of this thread, and she says,

"Instruments like humidity, they don't like dry. Unless you plan for the instrument to live in the desert in Australia, I really wouldn't worry much. Even if the instrument does ultimately go to live somewhere drier than where you are now, gradual acclimation to the new environment will usually prevent problems from developing."

If you would like to check out the kind of work she does and guitars she handles go here:

I just thought I would pass this along as one more bit of information beginners like me could take into account."

Aug 20, 07 | 4:08 pm
Bill Cory

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What this all tells me is that it's difficult to make any generalization where wood is concerned: Usually, it's going to react; sometimes it doesn't. Possibly, those vintage instruments were cared for when they were young, or they were built in an environment close to the average, as we have suggested -- there's no way of knowing. It's just a fact that wood will gain and lose moisture depending on its environment, and it's probably safer to build close to the mean than to build "wet" -- or "dry."

Prudence would say: Figure it's going to react to dryness and build accordingly.

Just my 2ยข.


Aug 20, 07 | 4:17 pm

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It seems to me, as a furniture builder now addicted to guitar making, that the very nature of guitar construction and design makes it difficult to plan for wood movement. There are cross-grain gluing situations, particularly with bracing, that we generally avoid in "normal" woodworking or use special joinery to make up for. We know that wood will expand and contract across the grain quite a bit but very little along the grain. We also know that flatsawn boards will generally move more than quartersawn boards. We also know that the degree of stiffness (thickness and bracing) affect tone and volume, but also affect flexibility and resistance to joint failure due to wood movement.

My apologies for this ramble, but my point is that these issues contribute to the fascination of lutherie as a craft. The goal is, as always, balance.


Aug 21, 07 | 7:52 am
Rick Homan

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Total Posts: 4
There is a relevant discussion of how humidity changes affect a guitar on's Luthier's corner. See "High Humidity, Problems at Lower, 06-25-2007." David LaPlante, Greg Mirken and Al Carruth discuss how a guitar built at 45% is affected by acclimation to 85%, and the effect of repeating this cycle.

Aug 26, 07 | 7:51 am
blues creek guitars Authorized Martin Repair Ctr

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Most hobby builders don't have the luxury of climate controlled conditions. In my early years I wanted to build in the summer in PA where humidity can be extreme and as Ken pointed out , cross grained gluing is just asking for disaster.
To help overcome this you can "cook" your plates before gluing bracing. I used to use my wifes cloths iron and would iron the plates for about 15 minutes. Amazing what will come out. This helped to heat out some moisture and de-stress the wood so that the radius of the braces could pull the plates. I also was lucky that once I started that I never had a joint fail . This helped allot to stabilize things.
IT isn't a substitute for climate control but will help to avoid that severely sunken top come winter. Also I agree that all guitars should be treated with respect and given the hydro or dampit treatment. They do save guitars . It isn't the wet it is the dry that will pull the guitar apart
john hall

Aug 26, 07 | 5:32 pm
Scott Whitney

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Total Posts: 6
Here is an inexpensive way to control your humidity. It is low tech, but it does work. Go to Radio Shack and buy their digital combination Thermometer / Hygrometer, catalog # 63-1032. Put it in your shop and watch the humidity readings for a few days. If you have low humidity, go to Walgreens, buy a cheap humidifier and one of those timers that plugs into a wall outlet. Set the timer to run for half an hour every day and plug the humidifier into the timer. Watch your humidity for a few days and adjust the run time as needed. You can do the same to decrease humidity by buying a de-himidifier and running it the same way. For less than $100 you can control your humidity better than most guitar retailers.

Oct 08, 07 | 8:53 pm

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This place is just chock full of great, usefull information. It is so refreshing in this day of proprietary information that so many people get together to share experiences and information to help newbies such as myself.
This thread is particularly helpful for me. In Ottawa we have wild swings in humidity. In summer and winter we can go from 70/80 - to 100 % humidity in a matter of hours. The winter can be very hard and extremely dry with central heating.
A couple of years ago I purloined a two foot thick and 2 and a hals fott diameter of clear maple. Put it in the basement for "safekeeping". Went to look at it three months pater in January and it had split nearly in half. So my plans for it's use changed.
Now for my kit I will have a hygrometer and humidifier in the basement to try and even out the humidity in the house. The basement is where I will be building the guitar. I will give the kit a weel or so to acclimate to the basement before starting the build.
Again - thanks so much for sharing your stories and knowledge.


Oct 12, 07 | 6:36 am

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Total Posts: 132
Cool! Another Ottawa member :) and I can relate to what he said about our humidity swings.. In the winter it's a constant battle to keep the humidity at a reasonable level. I used to have to a large salt water aquarium that was loosing gallons of of water a day due to evaporation and my house was still bone dry in the winter. This winter will be exceptionally hard because I shut down and sold the aquarium about a month ago.

In my basement workshop room I have a humidifier for the winter and a dehumidifier for the summer. I do all my gluing and wood/instrument storage there. I aim to keep that room around 45-50% humidity.
My 10x20 garage is my dust making room... I have all my power tools set up there for cutting, routing, sanding etc.. I don't control humidity out there but it is heated with a 4800W 220V heater and retains heat decently. I don't think the walls are very well insulated though, but it's a townhouse so I really only have one outside wall to worry about. I only heat the garage when I know I'm going to be working out there, so I don't store any expensive wood or do any gluing in the winter in the garage.

To add to (or hijack) the conversation here..
How quick does wood react to change in climates? For example when I take wood from the basement (humidity controlled) room and bring it out to the garage (not controlled) to cut/sand/shape etc.. am I taking any risks?


Oct 12, 07 | 9:51 am

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