Official Luthiers Forum!

Hi Guys:

I was thinking of spraying nitrocellulose over Systems 3 epoxy. Has any one done this with success? I believe some spray over some other brands. Is it better to spray sanding sealer then filler (waterbase), let dry and spray nitro?
I was thinking that the epoxy filling and sealing (one step) would be much faster? Is this a logical assumption?
Does anyone warm their lacquer up before spraying? I 've only use the KTM4 before on a guitar. I have sprayed nitrocellulose on furniture. I need some simple advice if it is out there to be had. Thanks.

I sprayed Nitro over Z-poxy, but it wasn't the Systems 3 Epoxy brand. But I'm sure nitro will have no problem over this epoxy. Just apply the epoxy until you have the pores filled, then let cure for 24 hours, then you can start spraying lacquer. Good luck!

Mike Doolin did an article in the GAL magazine last year in which he said that was the way he does his waterbased lacquer finishes.

I've used Bob Smith epoxy for filling and then sprayed nitro over it with no problems. I have some System 3, just haven't gotten around to using it yet.

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Dave Rector
Rector Guitars

If you have any concerns about nitro adhering to the epoxy spray two light coats of shellac over the epoxy, then apply the nitro over this seal coat. I always sand the fill level and seal coat with shellac prior to building the finish film. Be it nito,waterborn or varnish. Shellac adheres to pretty much anything and nito adheres to shellac very very well.

I forgot to mention, I usually sand the epoxy back to bare wood, just leaving the epoxy in the pores. Then I shoot a coat or two of Parks lacquer sanding sealer over that.

I haven't had any adhesion problems so far.

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Dave Rector
Rector Guitars

I sand down to near wood but no more. Using 220/300/400 grit. Then apply 2 light coats of shellac allow to harden for 48 hrs. Then very lightly spray with DA, allow to gas off. Then start to apply finish film. So you are not appling to the epoxy you are appling to the sanding sealer, what ever sanding sealer you use. I think that maybe some are thinking that the epoxy is both the filler and sealer. You may be able to do this, but I would not spray nitro directly to epoxy. I think the srink rate is too variable between the two. This is not an issue if you use the epoxy as filler. but IMO maybe if used as sealer. I hope I explained my thoughts clearly. After several strings on this subject I finaly came to the conclusion that some out there did not realize that there was a sanding sealer over the Z-poxy filler. My error in not making this clear.MichaelP38426.554849537

Michael, I am in full agreement with your post. I am not sure if I would trust the lacquer to adhere properly if the entire guitar was covered with epoxy.

It might work fine (maybe I should try a test board to see) since lacquer thinner will cut the epoxy. In other words, the thinner in the lacquer might soften the epoxy up enough to make it bond.

Can't be sure though cause I haven't tried it.

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Dave Rector
Rector Guitars

I bought the silica thickener to go with the Systems 3 epoxy from LMII. So of course I was thinking of using it. I also have the KTM9 as well as Mohawk instrument lacquer. I guess I have to many choices for finishing. I am finding it hard to make a decision of what to use. I did want to have a couple of nitrocellulose finished guitars before trying the new KTM9. Thanks for the info, I will try and make a decision from your answers. I will let you know how it goes. Tracy are you spraying over a epoxy sealer or are you filling with epoxy,then a sealer and finishing with nitocellulose?

I just finished 3 guitars using system 3 and KTM-9, once I got used to spraying the KTM I am very very happy with the results. One thing to note is DO NOT use shellac with Epoxy, they do not stick to each other at all. Mike Doolin talks about this as well, I shellac my tops after the rosette goes in but then it all gets sanded off before I put the epoxy on.

Just adding my $.02

Cheers

-Paul-

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-Paul-

Patriot Guitars

So Paul, do you also coat the tops of your guitars with epoxy?

I had been thinking of doing this but am having trouble deciding what effect it might have on the top.

Can you tell me if you think it makes a difference?

Thanks.

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Dave Rector
Rector Guitars

Paul In four years I have never had an issue with shellac not sticking to epoxy filler. This is news to me. If this was the case you could not use epoxy for filler on FP finishes. It is done all the time by may including myself. What am I missing here?MichaelP38427.4375115741

Dave...

Yes I put it on the tops, just a thin coat to color and fill, it's so thin that I can't see how it will effect the sound. The current guitar off the bench has epoxy on the top and it's a boomer so I'm pretty sure it's safe.

Michael I was passing along that info from Mike Doolin, maybe he can swing by and correct me but I distinctly remember him saying to use either shellac or epoxy but not both.

Cheers

-Paul-

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-Paul-

Patriot Guitars

Paul, I think it may very well be true that you do not want to apply an epoxy over dried and hardened shellac. There may very well be adhesion problems there. However appling shellac over epoxy is no issue IMO. I have been appling shellac seal coats over epoxy filler for some time, and have not had any failures of any kind. Heck I can get shellac to adherer to plate glass. I ‘m not wanting to be stubborn here but I believe that maybe you got it backward. Hope Mike is viewing. So he can set me straight if I am wrong.MichaelP38427.4554282407

I have a related question on the epoxy fill. Charles Fox told me that he applied epoxy to the entire guitar and after application he just wiped it off smooth with a paper towel.

I must be using the wron epoxy or something. It get real sticky, real quick. I've tried wiping it and just get stuck in it. I tried one this morning using a rag dampened with DA just to see if that helped. I think I just pulled all the epoxy out of the pores.

Anybody have any suggestions on this?

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Dave Rector
Rector Guitars

I can't picture wiping off with a paper towel. The good news is you can sand back the mess and re-apply. I have the best results with a single edge razor blade with the corners rounded to eliminate gouging. I work about a 2" square area at a time till I have coverage. Allow to cure at least over night then sand level with the wood and repeat if pourious wood. It would seem to me that the issue you ran into would be un-avoidable with paper towels. and I am using Zpoxy finishing resign not the 15min or 5min epoxy. However they will work but the pot life is very short which is a large part of the problem you ran into.MichaelP38427.6646875

Dave, are you sure he was using epoxy. Sounds like a method I heard for filling pores with CA.

Bruce, he said it was epoxy. He even brought out a couple bottles of System 3 to show us. He said he used 2 different type of epoxy but I can't remember the details.

Gotta learn to take better notes, gotta learn to take better notes, gotta learn to take better notes.......

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Dave Rector
Rector Guitars