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?

[johnparchem]

What kind of low spots? I sand spruce across the grain so that I do not get ridges that are formed from the softer and harder grain lines. Scraping spruce also results in ridge lines. I have also found a random orbital sander helps get the top smooth. I would hate to put epoxy on the top, but I have never tried it. I spend extra time on my bridges to remove 5-7 grams, I would hate to add it back as epoxy.

[Craig Bumgarner]

What kind of low spots?

Small individual spots in the soft grain. Can't be more than a few hundredths of a millimeter. Probably dig out from initial heavier sanding and scraping. In spite of careful sanding with progressive grits to 1000, very hard to see until the first couple coats of shellac are on, then it is too late to do anything but progress with shellac. Which does work, but I'm spending a lot of time filling them up with multiple sessions of shellac. The areas without these spots were done a long time ago.

I've never had this problem with anything other than Lutz. No problem with sitka, romanian, englemann or cedar.

Regards the 5 grams, I'd rather not as well. It is distributed thoughout the top, so it should not have the same effect as 5 grams +/- in a bridge.

[kiwigeo]

Epoxy sets hard......I wouldn't use it on a top. I'd persevere and just keep bodying up the low spots. Its a bit like hand bending venetian cutaways...you just keep going till its done.

[Nick]

Its a bit like hand bending venetian cutaways...you just keep going till its done.

So about five minutes then?

I've often wondered about grain fill on the soundboard but then I think about the amount of time I've spent getting this thing to vibrate at it's optimum and then to possibly ruin that by sticking something as hard as epoxy into it? hmmmm Don't know if the old egg albumin trick would be a possibility? I've never heard of anybody grainfilling a soundboard but would be interested to hear of anybody that has and their conclusions as to the pro's and cons?

[kpcart]

no problem with usuing epoxy for spot damage - but not for filling all across the soundboard.
if you are french polishing, maybe do the old pummice filling technique? there are a few videos on youtube, i know people who restore old instruments (ie 19th century guitars) - that have scratches, they will pummice fill, rather then sanding off extra wood.