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This is sunken along grain lines. How do I avoid this?
The finish is em6000.
Any help is appreciated. Very frustrating







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What is your total prep/finish sequence? I'm guessing there's a scraper involved? Sandpaper creates the opposite problem of raised grain lines, so you could run some experiments, scraping and then sanding with different grits to find the one that best levels the surface without going too far.

With shellac, a couple repetitions of coating and light scraping will create a flat surface. It penetrates slightly and hardens the wood so it works more evenly. But personally I prefer the corduroy texture and try to preserve it if possible.

Does the photo show the finish after final buffing or is this a prior intermediate step in the finishing process?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

drop fill .
also what sealer did you use?

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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

I would guess that you had some grain tear out at some point. Possibly when pulling up some masking tape during binding installation? Then the depressions were not filled adequately during finishing. You can see these depressions during intermediary sanding of finish coats if you look closely and use drop fills to bring up the finish as John indicated.

OK, another question about the photo. Is the sunken finish along the grain lines limited to just in that one spot shown in the reflection in the photo, or is it distributed across the top?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

It’s in the grain lines


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To answer some of the questions about the finishing
I normally do 2-3 finish sandings raising the grain
I have use a few coats of shellac as a sealer
The lacquer is em6000

It appears the finish just doesn’t cover along some of the grain lines in the top.(looks a lot like open pores, it it’s spruce)


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At some point, you would have level sanded the finish before the final sanding and polishing. If the finish was sunken along grain lines, you should have been able to see it then because there would have been shiny spots corresponding to the grain lines. Did the finish sand completely level, meaning that here were no remaining shiny spots corresponding to the grain lines? At what point in the finish process did the sunken finish along the grain lines first become visible?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

M still learning how to do finishing... it’s a process in and of itself! I did level sand, but I should have seen such spots and corrected them at that point.

At this point I’m just wondering “why” this happens... why does the finish sink along my grain lines in places, does it have to do with not doing a proper sanding sealer?


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The very reason I've been asking questions is to get at the "why this happens".

Your last post suggests that after level sanding, the surface was flat with no sunken finish along the grain lines. Which indicates that the finish was level at that point, which suggests that the sinking along the grain lines happened later.

Did you level sand the finish before or after the finish was cured? How long did the finish cure before final sanding and polishing?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

If it looked good all the way to the buffer, is there a heat situation happening at the buffer?

Sorry that happened, hope you get it sorted out!


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Perhaps the subsidence is the offspring of insufficient wait between applying and leveling the finish? Finish was level but shrank (cured) afterwards?

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Peter Havriluk

This is what I've been wondering. EM6000 takes a fair while to cure thoroughly (three or more weeks). If the finish was leveled shortly after application, and the surface of the top wasn't dead flat before finish application, there could be shrink back after a few weeks of curing that would result in shrink back that shows the grain.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I've done mainly violins, and finally getting better finishes. I do a lot of things, the ground coat that violin makers talk about, before actually varnishing. Prep, but with stuff. People mentioned shellac. I use that, or fir resin (because I have it), and other resins in alcohol to seal the grain somewhat.

Then I do humidity cycling. Wet from the alcohol/resin, into a Lightbox, or the sunshine.

It ALWAYS raises grain. I use horsetail to smooth up, because it grows in my yard. I use it dry until the varnish is built up. I works like a very fine file, but sandpaper works too, backed with an eraser or something. I do this several times before it finally starts to have a hard surface that is just barely past wood. The violin I'm doing now, is about there, but it isn't smooth all the way. But on violins I'm not looking for a guitar finish. Even on the guitar, it's supposed to be a Strad, so it is smooth, and pretty flat, but will take some polishing maybe after a few months to get really hard to get guitar-like. The cedar belly doesn't have much corduroy, but the grain is so fine, there isn't much.

I might leave it in the box for several days, or bring it in, get it wet, and put it back out. It might take a week of two. Then, I'll varnish. I use oil varnish I made, but it will work under anything. Even after all that wet/dry/sand, wet/dry/sand, it will still not be completely smooth. My varnish is not self-leveling, and will dip into any hole or crevice, even though it is fairly thick, even without any thinners. I put it on with my fingers usually, and try to smooth it out when it makes a noise like sliding on wet rubber, before it won't move anymore!

It's pretty much prep work. It takes way more than you think. Not the same as what guitar makers do I guess, but it's what I do. French polish looks like it gets really smooth too. I don't know if people ever put varnish over that though.

I did use Z-poxy on my Archtop, and it worked better than anything for filling dips and holes, but it dries S O S L O W L Y. and it didn't like the temperature in my house and basement in the winter. For a filler it would be great. I just don't like the slow dry time. The finish is good though, and seems pretty hard.

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Why be normal?

I can pretty well guarantee that the depressions were there all along and you simply missed it. When you are sanding you need to get out a magnifying glass and look at every square inch. My eyes aren't very good now so I use an Optivisor to inspect the finish.

Gorgeous instruments, Ken! I love one-piece flamed violin backs.

Here's my ideal soundboard finish. A sitka harp ukulele with the perfect balance of texture and shine. One of the few times I've gotten French polish to work properly. Usually I end up having to revert to simple wipe-on shellac finish which produces a mostly flat surface.

You have to apply your finish thick enough to level sand down to the lowest spots without sanding through.

https://www.acousticguitarforum.com/for ... 127&page=3

A blast from the past....

That’s an interesting comment from Alan. If anyone would know about scrapers...


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My finishes are thin and on the soundboard they look like the photo Dennis showed. That's the way I like it. Haven't heard any complaints from my clients either. Some people like them to be glass smooth and that requires a thicker finish, ok if that's what you want.

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Steve Smith
"Music is what feelings sound like"

You can get a glass smooth finish without it being thick. It takes a bit of practice though.

The OP's issue looks like it only occurs in one spot so it does look unintentional. If this was the look he was going for and it was consistent over the whole top, that would be fine. But I don't think that is the issue here.

That's true Barry and that was my goal early on. I should have been clearer in my post. After a fair amount of work I was able to get those smooth tops with a relatively thin finish but, in my experience, after a few years of playing out and humidity swings the tops weren't glass smooth anymore so I decided why fight it? Anyway, kind of like the semi-hemispherical fret ends I worked so hard on, none of my clients seemed to care.

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Steve Smith
"Music is what feelings sound like"