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For the last couple weeks my shop (garage) has been around 55% - 60% RH and this morning was hovering around 50% RH. Just now, 10:30 AM, I'm seeing 35% and dropping. Brutal, nothing to do but wait it out and this one should break fairly quickly.

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I lived in Southern California for many many years. The Santa Ana winds were always interesting, but I never really welcome them. The sudden dryness always seemed very odd.

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EddieLee

Great for surfing, but not so good for fires and humidity control.

Wow - down to 22%. Guess I'll glue my braces on another day. And will definitely surf in the morning.

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And here's an unbraced top left over night as the humidity fell. 1/2" minimum bow at the edges.

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I keep my unbraced tops and backs weighted until I brace or if they are in an environment where the humidity will change. I recently moved from Olympia, Washington to Phoenix and several survived. I now have a humidity controlled area and can stop stressing about it and start building again. Humidity here is typically around 20 or less.

i'm thinking that as the wood cells absorb water in high humidity conditions, the cells puff up and swell, and the wood it takes on the form of how it was when it was still alive, or "green", which is: straight(er).
...and when it dries out, the cells shrink, and the wood curls in one of more directions. is this at all true?

Wood typically warps with moisture as it affect each face differently. In the case described with the top laying face down the top of the piece was exposed to the lower humidity and shrinking more than the bottom face bowing the wood.

Just like an old board laying on the ground will cup with the moister lower plane expanding and dryer upper plane shrinking - I think.

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I was doing repairs and building at the New Expression back in 1981 and a Santa Ana blew in. One of my instruments developed a top crack hanging on the showroom wall. Bad memories.

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michael propsom
www.propsomguitars.com

Due to the Santa Ana winds, I find it a good idea to brace at no more than 30% humidity for a guitar intended to live in this area. I'm sure others disagree.

Greg...does that seem to work well? I am considering doing the same here in Phoenix area...of course if it will be staying here. It seems to stay in the 20 to 30% most of the time

Dave, yesterday in Phoenix it went down to 9% or 12%. I can't remember which. Don't expect it to stay around 20-30%. Last year I saw it go as low as 6%. In my opinion it is much easier to control than high humidity as long as you have a good humidifier.
Wendy

Wendy, I am in the process of getting a controlled assembly area set up and that will help quite a bit. I am considering building in the lower range if the instrument will be staying here. Seems less risky.

Yes it does. If you're not a factory, it makes more sense to me to build for the humidity of the intended environment. Anyway, that works for me, for So Cal weather.

No. Where do you come up with these ideas?

uh...because i have observed straight lengths of lumber warping as they become dry, and sometimes(in the case of a particular guitar neck) straighten out when the weather dampens....? if not, enlighten me, O Master, because i am here to learn.

Everything you ever wanted to know about warping wood.

http://www.woodweb.com/knowledge_base/W ... rying.html

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