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Hey everyone, been a little while since I last checked in. Finished the electric, onto the acoustic.

Six weeks or so ago, I bought a set of cocobolo rosewood back and sides. When I received them, I unpackaged them, set them on the work bench, nice dry conditioned environment. A couple days later, I discovered that the pieces had all started to warp, and promptly placed them under some weight. What I assume happened was that they picked up moisture during shipping, and when drying out again, decided to curl up.

Fast forward to today, checked up on the pieces; The two side pieces are nice and flat, one of the back halves is flat, but the other halve is still somewhat warped, in such a way where the middle is mostly flat, but the outsides are curved up somewhat. The thickness of the piece is about 1/4".

Is there a way to go about correcting this? Good grief I really hope there is. If that half is unusable my whole project is heading in the scrap direction, the neck is currently being built to match. Any help would be very much appreciated!

Flip it over.
Seriously. The wood is trying to reach equilibrium with its new home. If you sticker it and put a fan on it, it should flatten out.
Or just keep flipping the wood until it stays flat after the last flip. The bench side of the wood can't gain or lose moisture while the exposed side can so it cups.
Got it?

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http://www.CostaGuitars.com
PMoMC

Yup, got it. I should have remembered my dad's old advice, "Can't solve a problem? Just turn the whole thing upside down, and try again."

It's flipped and weighted, hopefully should straighten it out.

Good advice! If it doesn't flatten out, there are other options but hopefully it's just drying out.

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http://www.CostaGuitars.com
PMoMC

I know it's a somewhat ambiguous question, but how long does it take for it to reach equilibrium? It's not a particularly thick piece of wood, so I wouldn't think too long?

If it doesn't start to show signs of flattening in a few days, I'll pop back in and see what my other options are.

It should happen pretty quickly unless the RH in your shop keeps fluctuating. I'd say a day or two if you keep flipping it every hour or so. The weights will only prevent you from seeing that it has begun to cup and they are also covering the wood so the air can't get to it on the side facing up.
I would remove the weights and see what is happening. Each time the wood cups, flip it. If one half of the back is flat and the other half is not, I would suspect the wood is stable but is cupping due to the RH change from one side of the wood to the other. You could also put the wood up on blocks and put a fan on it on low speed so the air blows gently on both sides of the wood. That will speed up the process.
However, if you don't have the humidity in your shop controlled in some way, the wood will want to do this each time the RH changes, which is daily.
Where do you live and what is the RH in your area this time of year? I'm in New York City and it is humid as can be this time of year. If I take wood out of my stash that has been covered on both sides, it will curl like a potato chip. If the wood is stickered with a fan on it, it does not curl. But, I only sticker the wood I plan to use in the next couple of months. Everything else is just stacked without stickers.

_________________
http://www.CostaGuitars.com
PMoMC

I'm living in Rochester, NY at the moment, with the shop in the basement. The environment is pretty stable I would say, dehumidifier is usually going, temperature at around 68 degrees or so.

Took the wood out from under the weights, and stickered it, shown below. Hopefully that's an appropriate stick spacing. I placed the cupped side down on the pieces that were suspect, and set the fan at a low speed. I should see a change in pretty short order, yeah? I have a sneaking suspicion though that this isn't going to solve the issue.

Thoughts?

It should change quickly under those conditions. If not, then you move on to heat. An iron, yes the one for your clothes, then weight. It's strange that one half is flat and the other is so cupped though.

_________________
http://www.CostaGuitars.com
PMoMC

I checked today, it does seem more flat, but still cupped. I'll take it out completely tomorrow and see how it looks.

And that was going to be my next question about using heat. How do you go about doing that exactly? Just use it like a normal iron to wet and heat it, and sticker it again? Lay a thin cloth on top as not to burn I'm assuming?

I've only ever heard about it so I'm not qualified to explain the procedure but I would heat it wet and then sticker it again with weights.

_________________
http://www.CostaGuitars.com
PMoMC

Spay each piece with water both sides and sticker them.

Place a piece of stickered plywood on the top piece to stop it drying out on the top.

No need for weights

J

PS use smaller pieces of wood for stickers 1/4" square max should be enough

I tried to flatten it out by spraying a bit of water, and then stickering, not a whole lot of luck.

So I ended up soaking it for a half an hour or so, then stickered it, then on the top board placed six salt blocks. Took a look at it again today, it had flattened out nicely! Thanks everyone, let the building continue!

I'm glad it worked out for you.

_________________
http://www.CostaGuitars.com
PMoMC

heat yes water know. Often water will make the problem worse. If it is mildly cupped the braces will hold it in place but a nice example of stickering. Always stack your wood and keep it weighted.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it