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Anyone on here spray polyester? I've got a guitar that I sprayed just a few thin coats of satin precat lacquer onto. So it's a very open grain and simple finish. The customer is now curious if I could build up a thicker finish with filled pores. I typically don't use pore filler and instead use Simtec polyester sanding sealer for base coats /grain fill to level the surface. Once that's done I'll spray lacquer coats over the top.

Do you think I could spray polyester over these thin coats of precat lacquer that are already on the guitar? I would spray a few coats of the polyester, get a level surface and then spray another coat or two of satin precat lacquer over the top. Think there might be adhesion problems between the polyester and the lacquer or would it be just fine? I know for sure that lacquer over polyester is just fine but I wasn't sure if you could do the opposite with lacquer sprayed first and polyester on top.

I have never tried it so I don't know, but...

Even if others have had success doing poly over lacquer, your success will depend on using the same materials and methods. There is a very wide difference within the ranks of polyester and lacquer finishes.

I would try a test first. I would do a sample piece, doing it the same as the existing guitar finish. Then I would divide the sample into sections and try different materials/methods until I got the results I wanted.

Good luck!

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Joe Beaver
Maker of Sawdust

I'm inclined to think it may work just fine as long as the precat lacquer is fully cured. But I'm not positive.

James, I have never tried to top lacquer with polyester but I would think it would not work well. Like you, I have topped cured polyester with lacquer and urethane but not the other way around. Maybe if you were able to seal the lacquer with an isolante, or barrier coater or polyester sealer like you usually use to seal exotic woods, the polyester would lay on there. As usual, an actual spray test is going to be your best friend.

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jw ( o)===:::

Could very well be right. Precats are an ever evolving finish. If yours is a newer version and has dried and finished cross linking it might just work.

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Joe Beaver
Maker of Sawdust

A few thin coats will sand off pretty quickly. Then you know what the finish will do. Adhesion problems sometimes take time to appear. I recently had my car repainted because the clear coat peeled off the color coat in places after 6 years. The paint shop honored their lifetime warranty, so it was free except for the aggravation of being without a car for a week.

The polyester product I want to spray onto the lacquer is a sealer polyester. It is Simtec 28x50 sanding sealer. I would then lay down just a couple topcoats of precat over the simtec. So the final result would be precat lacquer - polyester sanding sealer - precat lacquer topcoat.

Alternatively, if I decide that spraying the polyester sealer is too risky, I am considering spraying vinyl sealer over the current precat coating. And then topcoat with another couple coats of precat. Should a lacquer based vinyl sealer be ok to spray over precat lacquer?

The questions you ask have no ready answers...as there is too much difference between "lacquers" from different companies these days......Some are very stable when stacked with dissimilar coatings, others give up right away and then there are those that only fail 6 months to a year out. The only way to be sure is to run long term test panels....or go back to a tried and true system.

I would not spray Simtec directly over any type of lacquer, precat or otherwise....I expect it will delaminate at some point. You could seal it with an Isolante. I do that sometimes when for whatever reason I cannot completely strip an old finish....My process would be to strip off the precat and start with white wood and your regular full fill process. Precat lacquer will usually come right off with some acetone and steel wool.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Very good advice. My concern if I strip the lacquer with acetone is that it will rob the figured redwood of its color. Would scrubbing that much acetone onto the surface pull a lot of color out of the wood?

"Very good advice. My concern if I strip the lacquer with acetone is that it will rob the figured redwood of its color. Would scrubbing that much acetone onto the surface pull a lot of color out of the wood?"

Actually it might put some "color" into the end grain portion of the "figured" wood. Additional applications would probably clean it up though. If you only have a few light coats of finish on the surface using a fine grit sandpaper might be less messy. For thick finishes I have used solvents to strip them, but almost always, then lightly sand the bare wood afterwards.

IME acetone doesn't lighten wood in color, even the cocobolo where the rag comes off brown with oil from the wood and the wood itself doesn't lighten in color.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/