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I recently finished a wide-grained ukulele, and something happened that I can't seem to fix.

Here's how I did it:
I sanded the body, raised the grain, and sanded again.
I stained the body with water-based black stain several times to get a good dark appearance. I lightly sanded to get any other grain that might have raised from the application.
Using the Stew-Mac water-based lacquers, and I applied my sanding sealer and sanded several times (8 or 9 good coats).
I applied 5-6 coats of topcoat lacquer.
I let it sit for 7+ days.
Started sanding with 1000 grit. Here's the problem: Upon sanding I filled small holes in the body with lacquer dust. Removing these spots has become a task. I have worked my way back down to 400 grit sanding quite a bit, used 50% water / 50% denatured alcohol mixture to clean the holes, and even added another coat of lacquer hoping to "wet up" the holes and maybe eliminate the white spot on my black stained guitar.
Now, I will say that I did not plan on making this a "glassy-smooth" finish. I planned on having some grain show. Basically it is an experiment to see how it would work.

I'd like to hear some opinions on what I did wrong to create these white spots on my black instrument. My guess is that if I stain an instrument black, I need to prepare to make a glassy finish so this won't happen again.
And . .. .I did use clear lacquer. A tinted lacquer would have made the "lacquer" dust dark, and this problem wouldn't have occurred?

As of now, my wife says it looks "stressed," like furniture one buys.

Any ideas/comments would help. This doesn't seem to occur to such an obvious level when I use other "lighter" colors of stain, by the way.

Thanks a Bunch!

Are the "white spots" the pores?

Sometimes, if you sand the lacquer and pores are open, the powdered lacquer will pack into the pores. If you shoot a coat over this, the powdered lacquer in the pores will remain white and be locked in between the coats.

I've never heard of mixing alcohol and water to sand with, but I don't shoot water based either, so the above may be wrong, but it is my guess, based on what I have observed with nitro....

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Brad Tucker

My friend a picture would be really helpful? Thanks.

Not sure if Naptha is compatible with water-based but I wipe up with a paper towel wetted with naptha several times after each sanding session. This pulls most of it out. If naptha won't dissolve your stuff it should work too but not after it has been trapped between coats I don't think.

Best of luck.
SR

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"We might not be big but we sure are slow"

Seems to me you missed the grain filling step.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

It would seem to me that sence you did not pore fill, as you sanded waterborne acrylic lacquer dust got into the pores. You did not say you used compressed air to clean off the surfaces but use water DA mixture. This may have wetted the dust but did not removed it completely. Then when over coated the over coat slightly bridged the remaining dust left in the pores but did not burn into the dust. Once the finished gassed off, the spots returned. If I am right the spots are under your top coats. Waterborne acrylic lacquer does not burn in quite the same as nitro. In fact not nearly like nitro.

My personal opinion waterborne is not the best choice for a non- pore filled finish for just this kind of problem.

Thanks for the advice.

The dust is in select "low" points in my ukulele body created by the grain not being filled. It's not in every low spot, but it's in a substancial portion in some locations which occur over about 50% of the ukulele body.

I am using compressed air and should have blown the body. I'll need to find something to clean it with if naptha isn't the answer. Yes, the last top coat pretty much sealed my fate (no pun intended).

This scenario will play itself again on another instrument I'm working on right now. I'll add a few more top coats to fill those low spots before sanding. I'll need to abrade the surface since I've already let it 'burn-in' for a week or so. If I use a coarser grit, I can hopefully increase the size of my lacquer dust and be able to clean it out.

The DA/water mixture was offered as a suggestion from a hobby furniture finisher.

I need to find out if Naptha can be used on water-based lacquer. If not, what is the water-based world equivalent?

I use naptha all the time on KTM 9 with no issue. I would not mix it into the waterborn but it will not harm dried waterborne