Official Luthiers Forum!

I've been using Sherwin-Williams vinyl sealer as a base coat (under nictrocellulose) for over 20 years. It has 24% solids and fills nicely, but it's now gone up to nearly $56 plus tax.

How many of you--who finish with nitrocellulose--use a different brand vinyl sealer--or a sanding sealer? Also, you who use a premixed shellac, what brand do you use? And to all who reply, how many coats of your respective product do you apply before going to the nitrocellulose?

Thanks to all in advance.

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michael propsom
www.propsomguitars.com

I found that mixing the brands often tends to have issues later. I use the same brand sealers and nitro . Behlen and SW you get what you pay for

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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 usually use shellac. Zinsser's seal coat to be exact, but I've also had good luck just starting with a thinned coat of lacquer. To me $56 a gallon doesn't sound high for a vinyl sealer, but 24% solids sounds high for a musical instrument sealer. Do you thin it before spraying? I'm just curious.

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

No sealer needed for nitro. It doesn't add anything positive to the result. You shouldn't need to fill with a sanding sealer if the surface is well prepped.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I use CF Martin's finish schedule and use the sealer between the filling process to avoid bleeding .

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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

Are you referring to epoxy or egg whites, etc?

I'm referring to flat. I raise grain with shellac, and then sand it back to wood before going to nitro.

Sanding sealer is designed to speed production in commercial shops by allowing for somewhat sloppy surface prep (i.e., scratches). It fills scratches and it is designed to sand better than plain lacquer (or whatever finish the sanding sealer is based on). So you spray it and then sand again to get a flatter surface. It does not improve the adhesion of lacquer to wood--on the contrary, it can hinder it. Other finishes may need a barrier coat on the wood, but nitro lacquer does not. Vinyl sanding sealer does not have the same problems with adhesion and translucency that stearated sanding sealer has, but it does nothing to improve the finish. When the manufacturers say you should use vinyl sealer with their musical instrument lacquer, they should add IF you choose to use a sanding sealer at all. But they don't mind selling you an extra product you don't really need.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Thanks all for the info. I actually sprayed my first fifteen or twenty guitars with straight nitro with no problems. Then, I read that lacquer didn't adhere well to bare wood, so I switched to a base coat of vinyl sealer. In retrospect, I have one of my first guitars from '79 and, other than myriad dings & scratches, the lacquer is still fine. Guess I'll go back to exclusively nitro finishes.

Thanks again, John, Woody and Howard.

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michael propsom
www.propsomguitars.com