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Posts: 2879
Joined: Jan. 30 2007
From: London (the South of it), England
Moisture warping
Hi.
I've been back to work for a while now. So guitar stuff has Kind of stopped. Plus the weather has changed drastically...So going out in the garage to work late in the evening or on a damp and cold weekend isn't that appeaLing. I finally looked in to the garage yesterday and the humidity was up in 80s and my back that was resting on the sIde, upright. Its warped, curvIng backwards.
😒
I've brought it inside. (And my top) will it unwarp? I think it has a little already overnIght. Is there anything I could do to help?
Thanks. Yes I have a dehumidifier. But hadn't had it running. My garage is pretty raw. A roof, walls and the door. No insulation. Gaps in the congregated roof eaves. (Gonna fill with foam)
I suppose a bit of dehumidifier will work but worried I'm just pissing into the wind so to speak. I mean is it worth running the thing before I seal up the garage a bit more??
If ai was in you I’d buy some foam cans and polystyrene to fill gaps and to layer the critical spots of the room. Next step is to seal the gaps in doors and windows and just eventually to add some rolls of insulation staff in your attic. The latter is the more expensive step and before starting I’d check if the previous action sorted something out.
Hi Stu. If the back and top haven’t been braced yet, then they can be brought into the house and stickered under weight until you’re ready to brace them. The sticks will allow air to circulate on both sides of the pieces so they can take on or release moisture evenly and will also encourage them to acclimatize straight.
If the back is propellered (I know that’s not a real word - potato chipped is another expression) it could be slightly dampened in the areas away from any glue seams and then stickered, but care should be exercised if this route is chosen. The propeller shape is likely in the wood itself so there’s only so much that can be done about it. You can assess it by holding the piece and twisting it - if it ‘sproings’ between propeller shapes then the grain of the wood itself holds the characteristic and it’s just there. To compensate, just make the bracing a little higher to allow for the stress and/or consider doing a four brace pattern. Some would recommend discarding the wood, but at this phase of your journey I think just use it and don’t stress too much about it.
If the top and back are already braced, then this points to a process issue, in that the bracing should only be done at the point just before the assembly phase. So, sides should be bent, liners prepared, everything should be ready, then glue on the braces, carve, and assemble the body as soon as possible after that. Generally it’s good to try to do all this over the course of a few days, if possible. Especially when done during a change of season, there is more wiggle room when the work is done mid-season.
It’s never the end of the world. If the pieces are already braced then acclimatize them and consider making forms to place under the pre-shaped bracing to encourage the pieces to return to where they should be. If building top down, the sides can be attached to the top with a form or weight sitting on the top in the bridge area, to push it in the right direction. If really bad, the back braces can be planed off and the back re-braced, this should be considered in any case where a large brace is warped, as the brace itself is compromised. There’s no harm in doing something over. After all, what’s a day or two’s extra effort in the life of a guitar?
Yes thanks echi. I have the stuff coming in the mail to seal all the offensive areas.
Thanks Rob for you thorough reply.
The back is braced. And the braces are fine. I made them rather thick and they don't seem to be compromised. The curve dictated by the radius on the braces had remained. But the warpung seems to be along the back strip. So cording backwards so to speak. I guess this is what you mean by.propellar? Or would that be off it was twisted ....
Thanks for the info regarding time between bracing and building. I did my back a while back. Mainly due to not having anything else I could get on with at the time. (Was waiting for stuff in the mail) Good to know though thanks.
It doesn’t sound like it’s propellered, it sounds like it was resting with the braced side facing out and the good side restricted from receiving air flow. Propellering is a twist from one corner to the opposite, like a blade of a propeller, and is due to inherent stresses in the wood, not from environmental reasons.
I don’t think this is a big deal if the integrity of the braces is OK. Once the back is put onto the sides everything should push back into the right direction as the arc of the bracing will force it that way. Maybe rest the back brace side down for a bit. This will allow the opposite side to get more moisture from the air and it might help move the curve back to the intended side.
I’ve had stuff move funny in the past and went ahead with the assembly without issue. But, it was enough to convince me to adopt a process where the bracing to boxing operations are done in a short window of time and I try to avoid leaving braced elements hanging around loose for very long.
After I was laid out this April a had an unbraced but centerstripped back get wonky. I had wiped about four coats of shellac to the outside. I had a top glued to the ribs and also a handful of shellac coats that tried to flip inside out once it warmed up in the summer, towards the end of summer we had some higher then usual humidity and it caused some trauma with the two guitars I had finished except for the shellac.
I just jigged up the top with some clamps to push it back out and placed the back on my string edged solera with some weight on it.
The two completed guitars I unstrung and have hanging in the shop without much humidity at the moment and both are back where they belong.
I keep a endgrain hygrometer I made in the shop and house to get a general idea about where the humidity is. I humidify as required in the winter months.
HR
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I prefer my flamenco guitar spicy, doesn't have to be fast, should have some meat on the bones, can be raw or well done, as long as it doesn't sound like it's turning green on an elevator floor.
Stu, Photo is business end of an end grain hygrometer. This one is a stack of end grain blocks glued in about 60cm strips in Spruce, Cottenwood, and Birch. These are the local woods I build with. On this one the strips are hanging from the top, as the expand they push down on the short lever arm of the pointer and the long arm us how it is read. A little more info on my Instagram:
Google end grain hygrometer and you will see all kinds of them. It's a fun simple shop project. It's not precise to a decimal place but once adjusted you will have a good idea of your shop or home humidity. Torres had a simple one in his shop and was said to assemble only when it pointed the way. It's sad, I've had way more interest in these then my guitars ;)
Photo is one I had fun with for a local woodworking buddies birthday gift.
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I prefer my flamenco guitar spicy, doesn't have to be fast, should have some meat on the bones, can be raw or well done, as long as it doesn't sound like it's turning green on an elevator floor.
I had to do the humidity sensitive glue ups in a spare bedroom inside the house. It was the only way I could really control the humidity. My go bar deck sits on the spare bed
That’s the most Rube Goldberg F-ing thing I’ve ever seen on a guitar Foro. You win.
Lucky!
Actually I gave it to my budy disassembled and he had to put it together. Was a fun test cause he had no idea what a hygrometer was, and you know me, I'm lucky I can spell it! He had it assmbeled and as his birthday party got to be more heated and dancing etc the needle slowly swung to the left. It was like a party game all in itself to see how far we could get the needle to move. Sure glad I didn't have a guitar at his house that night ;)
I had about an hour and a half before we had to drive over and two cut off pieces of the end grain blocks, light went on: pinion on top left, rocker both bottom ends, push up on short end of arm and half round joggle around hinge pin. Hammered electrical copper to look rustic, linseed oil on Hickory base. Works great.
I get a text from him with a whether update every once in a while.
One doesn't need a digital device that requires calibration, there just guidelines anyways.
HR
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I prefer my flamenco guitar spicy, doesn't have to be fast, should have some meat on the bones, can be raw or well done, as long as it doesn't sound like it's turning green on an elevator floor.
Small update on this for anyone who cares or more for me cos I'm feeling good about this!! ahha.
Ive been radiusing the sides ready for the back. I went in the house and got my once warped back. totally expecting it to be an absolute mess when i presented to the rest of the guitar in the mold....but I genuinely felt a buzz when it actually fits!! the signs of previous warping have either corrected or I was freaking out in the first place.
some pics. cos I feel quite proud!!
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Cheers rob! I'm not sure about the cypress. I bought it in 2015 from Maestro Stephen Hill in Granada, who I believe got it from Madinter. Maybe they get some up from Turkey?
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