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Temperature/Humidity and Storing Wood?
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Author:  PoppaWoodie [ Sat Apr 16, 2011 10:25 pm ]
Post subject:  Temperature/Humidity and Storing Wood?

I'd just like to preface this by saying sorry in advance for the stupid/newbie question. Haha.

I'm in the process of setting up my shop, and I'm building a couple shelves to use specifically for storing wood. I'm going to be stickering all of my back and side sets, and plan on storing them in the same room that I will be building my guitars in. What I was wondering is if there is a recommended temperature and humidity level to store back and side sets at? And should that temperature/humidity level be different than what it is in my shop/when I start using the wood to build?

I live in Western Canada where it can get very dry out, in case that has any effect on what humidity levels I should maintain.

Also, if you have any other advice on storing wood, it would be greatly appreciated!

Thanks a lot! :)

Author:  John Arnold [ Sun Apr 17, 2011 1:00 am ]
Post subject:  Re: Temperature/Humidity and Storing Wood?

Good plan, assuming the wood is seasoned. Stickering in the shop does allow the wood to achieve equilibrium much faster. The wood that I process is stored in the part of my shop that has no humidity control, and the MC never gets much below 10% there. For space reasons, my 'program' consists of bringing the body wood into the humidity-controlled area of my shop a few months before beginning the assembly. Even that is conservative, because 3/16" thick wood on 1/4" sticks will equalize with the surrounding air in a few days. You can prove it by laying the wood flat, exposing only the top side. If it is not in equilibrium, it will curl. Flipping it over will cause it to curl in the opposite direction. If you continue to flip it over until the curling stops, it has equalized with the RH in the surrounding air. The area where the guitars are assembled needs to have a stable relative humidity, preferably at or below the average RH where the guitar will live. I keep my RH around 40%, which translates to about 7% MC in the wood.
One note on stickering. If the top plate in the stack is exposed, it will curl during the equalization process, though not as much as when the wood is laid directly on a flat surface. That is because the air circulation is better on the exposed side. You can eliminate that problem by placing sticks on the top piece, then placing a scrap piece of wood on top of the stack.
Resist the urge to clamp or otherwise restrain the wood during the equalization. The curling happens because the MC is not evenly distributed through the wood, not because of uneven shrinkage that is normal during seasoning.
A box fan (even set on the lowest speed) placed on the wood will speed up the equalization process tremendously.

Author:  Andy Birko [ Sun Apr 17, 2011 6:50 am ]
Post subject:  Re: Temperature/Humidity and Storing Wood?

John Arnold wrote:

Resist the urge to clamp or otherwise restrain the wood during the equalization.


What bad things will happen if you simply can't resist the urge?

Author:  PoppaWoodie [ Sun Apr 17, 2011 1:44 pm ]
Post subject:  Re: Temperature/Humidity and Storing Wood?

Thanks, John! So, just to clarify, does that mean that I can leave the wood to season in a room that isn't humidity controlled, as long as I bring it into my shop and allow it to reach equilibrium before building with it?

Author:  John Arnold [ Sun Apr 17, 2011 9:07 pm ]
Post subject:  Re: Temperature/Humidity and Storing Wood?

Quote:
What bad things will happen if you simply can't resist the urge?

The wood can crack, and/or develop internal stresses. The main reason for cracks in a guitar is because the wood is restrained by the bracing and blocks. If the wood is free to move, there is no stress to cause cracking.
Quote:
So, just to clarify, does that mean that I can leave the wood to season in a room that isn't humidity controlled, as long as I bring it into my shop and allow it to reach equilibrium before building with it?

Exactly. Novice luthiers get uptight about storing wood, but as long as it is kept dry and away from excessive heat, it should be fine. It is only when you start assembling the guitar that you need to be concerned about humidity, because of the cross-grain construction.

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