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Would it be OK to use naptha to detect sandthroughs? I have a couple of washcoats of light blond shellac over some Koa to pop the grain. I am using waterbase grain filler over the shellac and I am getting a significant number of sandthroughs as I level the grain filler. The problem is that I usually can only tell that I sanded through the shellac after the next coat of grain filler. I was thinking that if I could wipe some naptha on after I sand the filler, I might be able to see the sandthrough and reshellac the area before the next coat of grain filler. Is this a good or bad idea? Any suggestions would be greatly appreciated.
Thanks,
Bill

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Formerly know as Mandodiddle.

I'd like to know the answer to this one too.....thanks for bringing the question up Bill

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 don't know about naptha, but I don't think another coat of shellac all over on top would harm anything before next grain filling?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Another wash coat of superblonde shellac will resolve the issue. You're not going to not sand through the sealer coat when you're leveling pore filler. Spray a light, but wet coat of shellac, scuff sand it and spray your top coats.

OK, thanks guys.
So if I'm understanding correctly:

After sanding back a grain filler coat I can just apply another wash coat of light blond shellac and then apply another grain filler coat. In other words - sand, shellac, grain filler, sand, shellac, grain filler and repeat this sequence until no more sandthroughs are seen?

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Formerly know as Mandodiddle.

I suppose I should ask what type finish you will use, but my understanding is if you finish after grain filling with a coat of shellac, pretty much anything will stick to it.
I've used an oil based filler with shellac over it, then waterbased top coats and had no problems with that.
Perhaps someone with more experience can confirm if this is correct.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Colin,
I will be using waterbase sanding sealer and top coats.

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Formerly know as Mandodiddle.

Bill, if you're pore filling apply the first coat and let it dry, apply a second coat, and let it dry -- if you feel you didn't get enough on the first time. Allow several days for the pore filler to dry and shrink before leveling. Blow out the dust with compressed air and wipe with a tack rag, then reseal. Apply your top coats.

Thanks David,
Is there any time limit between the last coat of waterbased grain filler and the shellac coat (If one applies a shellac coat also after the grain filler)? Likewise what about a time limit for applying waterbased sanding sealer after the last coat of shellac?

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Formerly know as Mandodiddle.

Bill, you want to seal the pore filler. Whether you're using a traditional filler, or epoxy, you need to seal the pore filler because you sealed the body first. This is to ensure that you have a uniform chatoyance. You really want to have pore filler dry for several days before leveling, whether its a waterborne pore filler or traditional solvent based silex pore filler. Epoxy does better with at least a full 24 hours before leveling, longer is better. Then you must shoot a coat of sealer, whatever you used for the undercoat.

As for drying time, that depends upon the nature of the sealer and what your top coat manufacturer recommends. Most want you to allow the sealer to dry completely and scuff sand before top coating. The waterborne finishes are essentially a varnish and want a mechanical bond, so you need to scuff sand the sealer coat before top coating. Let the shellac dry an hour or two before sanding. Three if you can stand it. It'll be dry to the touch in 20 minutes, but you want it to be DRY before sanding.

Blow off the surface, tack rag and shoot your top coats.

Thanks again David. I appreciate your time and expertise.
Bill

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Formerly know as Mandodiddle.