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About 6 months ago I tested 3 finishes (varnish, nitro, and wipe on poly) on small blocks of very curly maple and koa. I used Micro Mesh to bring them to a mirror finish. I just happened upon them today and noticed that the finish on every piece of wood now undulates with the curl underneath (Sorry, no pix). Is this common for highly figured wood? The wood was sanded dead flat up to 220 prior to finishing and I allowed all the pieces to harden for 6 weeks before using the Micro Mesh.
What happened?

Give us full details of your sanding method. Block used, paper, grit and how fine, with the grain, across the grain, random orbit sander, did you back the micro mesh.....this will help in the diagnosis.

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Humidity. DAMHIK.

Rod- Preppin Weapon, Norton 220 with the grain. Micro Mesh with the supplied hard rubber block.

two dogs-the pieces of wood were stored and finished around 45% RH, but were placed in an area that is not climate controlled about three months ago. I didn't think it would have such an effect. The pieces are still perfectly square. What is the humidity doing to the finish that would cause these ripples? If this is common and you were selling a guitar to someone who lived in a humid place, do you tell them that this is going to happen?

Hi Darren, I see from your zip that we share pretty much the same weather. I've experienced the exact same thing with some of the dozen or so ukes I've built out of curly koa. It's not the finish that's moving, it's the curls in the wood (IMO). Usually it happens when hanging nitro finished ukes in the shop for a month. It's reversable to a point by returning it to the same humidity as when it was sanded and finished. Try bringing the samples into the house for a week or so, making sure air can get to all sides. Good luck.

Steve

Thanks, Steve. I will put those pieces in the shop to see what happens. I googled this problem and it doesn't seem all too uncommon. I'd really like to know how the big guitar makers deal with this. Anyone know if they build in "wetter" rooms for products shipped to wetter climates?

If the finish is thin this is completely normal - its the same as the 'telegraphing' you see on spruce topped instruments.

Yeah, I agree with Tony.
This is utterly normal. The finish material is shrinking with the cure process, and what is underneath is "coming through".
The only way to minimize this is to let the finish cure for quite a long time before you level/polish.
And even then, you aren't going to prohibit that telegraphing completely.
I'm one of the fortunate ones--I rather like the look. Looks natural to me, and not like a decoupaged bar top.

Steve

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+1

Finish shrinks a bit, and the wood moves a bit.

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Thanks everyone! I'm relieved this is normal. Tell me, though, what percentage of your customers expect that mirror finish to last a long time? Given my reaction to those pieces of wood I finished, I can imagine the uninformed are quite upset to see something like that on a guitar that they paid thousands for. I trust you tell them upfront about what to expect with a guitar's finish over time?

Figured wood moves within its'self more than nonfigured wood when subjected to humity change and that is telegraphing through the thin finish and is normal. The reason for that is the fact that figure is runout which contracts and expands at a different rate than regular grain does when the humity changes.

Actually I think people expect that, particularly on a high end instrument. It will only stay level for a few days or weeks, and that is normal.

Anyways, if the guitar is shined up to a high gloss, it will remain glossy. Only a low-angle light inspection should reveal any telegraphing in the finish...

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