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I recently completed an all koa SJ. The koa is pretty figured. When I picked it up from a local finisher (one of 2 that I use) the top was concave. TO be sure, I did not give it to him like that. It took several days for the top to correct. I put strings on it and everything seems fine now, except the finish. The finish is fine, but the wood underneath it has become wavy, very wavy. If you run your hand over it you can easily feel the valleys and ridges. I think this happened as the wood re-acclimated after the serious dry out at the finisher's. In addition to feeling it, you can easily see it. The waves are about 1/4 inch across and all over the top and back. The sides are not affected. I think it is because they are double sides.
The finisher says that is normal patina for high figured koa. It happens in time, this one just a little faster.
I’m thinking he caused and it would not have happened unless it was dried out.
What do you people with a lot of high figured koa experience say?
Thanks!

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

That's not "normal" for Koa or any other wood that I know of. If the wood is really dry (or really wet) when it's finished it will do crazy stuff under the finish.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

It sounds like your koa was not properly seasoned.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Agree with Laurent. You will probably have to sand back to bare wood, let it season properly (might have to take it apart and start over even!), then try again.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

I doubt the wood was not well seasoned. I bought the wood about 3 years ago from a reeputable supplier. It was stored at 45% RH in my shop. It was properly arched when it was delivered to the finisher. When I picked it up it was concave. The finsh was smooth. Sometime after the top returned to convex the finish started getting wavy.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

waterbased finish...?

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http://www.PeakeGuitars.com

Edit: Wow, then the finisher's environment must have been to blame....

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

I saw a Koa Taylor guitar at a store one time with the exact same defect as you describe.

No way!



The finisher claims that it just happens with koa. He said that most old koa guitars with high figure do that, it is in the nature of the wood. Can anyone confirm that?

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I doubt you'll find a definative answer. IMHO Koa has as much or more variation within the same species as any wood I know of. I've got a client with a ~10 year old Koa Taylor, as well as a 3 1/2 year old Koa that I built. They're both smooth as glass. He's a working musician so his guitars aren't always in a perfect envoriment.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Sounds like a humidity problem to me.
Does your finisher specialize in guitars, or automotive?
He most likely keeps his spray shop dehumidified, as it's easier to lay down finish in low humidity.
That would have no effect on metal parts dimensionally.
If it took him a while to get to your guitar it may have dried out.
Then he finished it and gave it back to you.
What's the humidity in your shop?
If it's high, then we know what happened.
It may not be his fault, if he's unaware of the effects of humidity on wooden guitar parts.
Your guitar dried out, the top sunk, got finished, swelled up again.
The finish kept one side of the wood smaller than the other, a wavy pattern developed as a result.
The dimensional changes were slow enough to prevent the finish from checking.

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Old growth, shmold growth!

I made a geet out of some highly figured mahogany about 5 years (?) ago,
and you can see and feel the valleys and ridges.
I had the wood for about 8 years before building, and it took a few years for it to get that way.
Nitro finish.
Strange problem, no?
Wood..........................................
How does it sound?
That's a lot more important,
especially to a musician.

He only does guitars, but much more electric than acoustic. I keep my shop at 35-45% RH.
I am certain that it got dried out at his shop. When I picked it up I commented on the concave top and told him that it could only happen if it dried out. He said it was in the drying room. He said that is to allow the finish to cure but that he keeps it humidified. I don't think it is humidified properly.
I'm pretty sure that this problem was caused by the poor treatment this guitar had, but not certain. I don't know if I should ask him to redo it or not and what percentage if any I should pay.
He does real good work and has done a few of mine in the past without issue.
Like Woody said - I do not have a definitive answer. I'd like one.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Ask him what the RH in his drying room is, and compare it to the outside "real world" RH, that'll tell you a lot. Guitars should be constructed in the 45% range.
When I was mainly building electrics, I didn't control my RH AT ALL and had no ill effects, even shipping from 70%RH to 35%RH from Florida to Ft. Worth, TX.
Acoustics are MUCH more sensitive to humidity changes than electrics, as their construction is much more delicate. The most responsive ones are built on the verge of collapse.
If your humidity is high, say in the sixties range, and his drying room is low, say in the 20's but he still considers that "humidified", then that could be an issue, I'm speculating.
Might want to ask him, if he's willing to divulge the info.

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Old growth, shmold growth!

If you built the guitar at 45%, then sent it for finishing at say 30%, then got it back and rehumidified it, there is no telling what figured wood will do ... it may or may not re arch, and ripples are par for the course, they wil start to show over time anyway as the wood moves thru the seasons, and handles the tensions in the guitar itself. I have a quilted maple guitar that was pretty flat years back when it was finished, but you can now see the ripples around the quilt figure in the back, and it has been at fairly consistant RH ... wood moves, ripples happen.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

You should check his humidity level with yours and see if there is a big difference. Maby take the same meter you use in your shop to his place to get an accurate reading on the difference. I would also think that figured wood would react to a difference more than non-figured wood. Curly maple does the same thing as it dries or seasons, but shouldn't move after seasoned and sanded level unless there is great humidity changes. The figured area or runout on figured wood expands at a different rate as the surrounding wood when subjected to humity and that is what you are seeing, but also happens as unseasoned wood dries out. More-so than unfigured wood does. Also, the longer the wood ages , the less this happens.