Official Luthiers Forum!

Ya know, I was just reading The Epoxy Book(available from System Three) a few days ago , and it mentions more than once how epoxy needs to be protected from UV. Epoxy breaks down completely with exposure. I didn't know that fact... Now, most of today's finishes have UV inhibitors, but none are 100%, and all lose effectiveness wit time.

They also mention that epoxy prevents full cure of polyester resins, and perhaps even break down cured polyester(something about amines not liking peroxides) wit time. I'm not remembering exactly, but the general thought that i came away with was that none of what I was reading makes me wish to use it on an instrument that has a life expectancy of hundreds of years....

Anyone else read that?

In my career, I've used McFadden's "mahogany" paste pore filler(2 thumbs up), LMI WaterBorne paste(9 thumbs down!), Target's WB filler(more thumbs down), shellac and pumice(many thumbs up), even shellac mixed with pumice as a paste and then colored, CA glue(thumbs up, but nasty fumes), but ya know, mostly, I've used the finish itself. Even nitro would fill nicely with just a few extra coats. and today, with polyester, geeze, what a no brainer that is... shoot 3 coats on the back and sides, let it cure 5-6 hours(MEKP/cobalt cured, a few minutes if you have UV <g>), sand 80% level, then top the whole body with the final 3 coats. Rick, I do it all in the same day. 100% filled, thin(especially on the top where it counts) and a one-day finish.

I pay a lot of attention to what the boat builders do, and yes, they have to protect epoxy from UV...along with everything else. But this is talking major UV exposure...outdoors, often in the tropics, way worse case than any of our instruments should ever be exposed to.

As for poly over epoxy...well, I don't...I put a barrier layer in between the epoxy and the polyester. That's what either Isolante or McFadden's rosewood sealer is about...isolating the polyester from any chemicals that inhibit cure. They are urethanes, and boat builders have been using polyurethanes over WEST epoxy built boats for decades now.

Go over to the Smith and Co. site and read up on what Steve Smith says about using epoxy as a wood sealer in exterior applications. Very interesting...

Grumps do you use isolante sealer under the first 3 coats?So 6 coats of polyester in 1 day,Sounds really effecient.Are you using an HVLP system? I guess I`m gonna have to give polyester a try.
James

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James W Bolan
Nashville Tennessee

Yes on the Isolante. No way to not use it...

It's not an efficiency thing on my part. It's dry enough to sand in 5-6 hours, and with the Chemcraft, I can shoot coats at 20 minute intervals. Including the Isolate coat, the dry time, the sanding, it all fits within a 8 hour day if it's the first and last things you do. Easily fits within my 14 hour days

Thanks for the input grumps.I always enjoy and pay close attention to your posts.
James

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James W Bolan
Nashville Tennessee

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Very Interesting topic... from a really simple question too!

Rick, how long have you been using the method you have been using? Do you have any "aged" guitars that have seen some use "in the field" to see how this finishing process holds up over a good portion of time?


I know that California has some extremely strict environmental laws. Is the reason you are using this method in any way a product of some of those laws? In other words, if you lived in a different state or country and environmental issues werent in the picture, would you do anything different?

I am particularly interested in what the vinyl sealer does to the wood and if this causes the finish to "slip" (for the lack of a better word for it) in years to come.

Just for the record and to let you know I'm not trying to be biased in this, I have the same questions about the epoxy pore fillers too. I think I have the same questions about this as Mario does.... the long term effects...

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Reguards,

Ken H

I've been using polyester on electric guitars since 1990 and on acoustics since '97. The early ones were done by a subcontractor down in Van Nuys, and he shot too thick, but they look OK. I started shooting the stuff myself in '97, and they still look great, though my technique has improved, and the epoxy pore filler is a major step forward.

We can shoot nitro, and Addam Stark does a lot of that in my booth. It's not the issue that out of state folks think it is, especially for a company my size. A couple of weeks ago the Air Quality Management inspector actually told Addam that no permit applications for spray booths were being turned down in this county right now because we're all so far under the problem level with VOCs.

I don't use vinyl sealer, but what I do know is that my finish system yields incredible adhesion...far better than most nitro jobs I see. I think vinyl sealer has been over-sold, and if you're going to shoot nitro, then shellac is a better sealer.

he shellac / pumice as a slurry or via

Yes. Lotsa pumice, lotsa shellac(forget pound mixes, I'd just make it fairly thick), and rub it around. It will pick up the wood's color by grabbing some oils and whatnot, as well as fine dust. In fact, I'd also not blow off the last sanding's dust and use that also. Once there's a nice slurry going on, stop, let it dry overnight, then come back and sand it back decently level with 150 grit, and topcoat.

Try it on some scraps, you'll see. Only caveat is that with rosewoods, all white fiber ad/or maple purflings/bindings will be dyed purple/blue. Not good <g> Plastics are easy to clean up, but forget maple or white fiber! Mahogany was fine...

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