Epoxy fill top before shellac?

[Craig Bumgarner]

Need a reality check. Would it be crazy to epoxy fill a spruce top before French polish? I'm using Lutz and this is my fifth guitar with it. Love it, but the soft grain is so soft that no matter the amount of sanding, I seem to end up with some low spots. If I start with shellac, it is a long road to filling these low spots, lots of shellac applied and eventually the color gets a bit mottled. So, I'm thinking of a single tight fill and squeegee off with clear epoxy. I've done this lots of times for grain fill on back, sides and neck, so technique isn't the question.

The question is how much might a thin coat of epoxy affect the sound. I typically use 5 grams of epoxy per coat to fill a back, so the weight distributed over the entire top does not seem like much. I'd be surprised if there was much stiffening effect, but I would not mind if it happened. I should think the dampening effect of epoxy would be less other materials I might consider for this such as varnish.

Thoughts? Is anyone doing this?

[Barry Daniels]

It won't affect the sound if you use a thin coat, but it really is not necessary because spruce is closed pore. Also, test on scrap first to ensure compatibility.

[Craig Bumgarner]

It won't affect the sound if you use a thin coat, but it really is not necessary because spruce is closed pore. Also, test on scrap first to ensure compatibility.

Right, but it is not a pore problem per se, more just some random low spots, just a few thousandths in the soft grain, probably torn out during earlier sanding and scraping. In spite of progressive sanding with 1000 grit, I don't seem to get rid of them and more importantly, they are very hard to see. The top surface looks great, but after a couple coats of shellac, I start seeing these spots and long after the rest of the top is done, I'm doing multiple session to fill up.

I've never had this problem with anything other than Lutz. No problem with Sitka, Romanian, Englemann or WR cedar.

Not worried about compatibility as I shellac over epoxy filled back, sides & neck all the time.

[Barry Daniels]

Sounds like you need a harder sanding block.

[Bryan Bear]

Your last post made it sound like you were planning to epoxy over the shellac that is already on the top. Your first post said you were thinking of doing it before you french polish. I'm probably just misunderstanding your last post, but if not. . . As I understand it, shellac will stick to a epoxy porefilled surface but epoxy will not adhere well to a shellacked surface. I've never tried, but that is what I have read. I figured I had better mention it. . .

[Craig Bumgarner]

Bryan,

Right, I'm not putting epoxy over shellac.

Barry,

I agree, I just have to be more careful with sanding. I sanded out a closed body today and was extra careful with it and being very thorough, I think this will solve most of the problem and then work the rest out in the FP process.

I've heard no one say they are, have or would epoxy a top and I respect that. Thanks for considering and your opinions all.

[Bryan Bear]

BTW, I forgot to thank you for mentioning the tendency for this to happen with Lutz. I have never used it before but have several sets in the stash. I'll know to be extra careful sanding.

[Barry Daniels]

I used an epoxy sealer on the top of my first guitar, so it can work.

[Bill Raymond]

As I recall, Don Teeter discusses the use of epoxy as a sealer coat in his book on guitar repair; you may want to check there. I believe he was thinning the epoxy with alcohol and applying with a tampon or muneca. Apparently he felt that the spruce on old Martins he refinished was a bit porous and benefited from a sealer coat.

[Michael Lewis]

A question regarding your low areas: what do you think is causing them? Also how big are they? Is this compressed fibers between the 'reeds' ? If so, I think you will benefit from raising the grain with water before applying any finishing material.

[Michael Lazar]

I've built more than 20 guitars with lutz tops with never a problem. It's better to work with than some of the softer spruces like Engelmann although I don't really have any problems with that either. One thing I've been doing for a few years is finish sanding my tops across the grain starting with 120 grit and working through to 320. Two things result. First, the initial coats of shellac seems to adhere more evenly with fewer "dry" spots. Secondly the finished result seems to have a "sparkle" with enhanced cross grain silk visibility. This idea is not mine by the way. I got it from Eugene Clark's writings on french polishing.