Guitar finishing help

[germdoc]

I am in the last stages of completing a guitar--classical style, from Grizzly kit. So far, so good--it's a nice introduction to guitar-making.

I am finishing with Behlen's instrument lacquer--according to recommendations, I applied 5 coats at full strength, then wet-sanded with 320 and 600-grit sandpaper, then applied another coat at 1:1 ratio with lacquer thinner. (I applied with a brush for reasons of convenience.) For some reason the finish is splotchy--several areas dried quickly and remain opaque, not glossy.

I'm not sure why that happened, but I'd like to even out the finish and restore the gloss. What should be best way to do this: polish with automotive polisher, rub with paste wax, +/- wet sand again (to 600 or 1200 grit?) or use steel wool?

Any thoughts?

Any ideas on future guitar projects? What is best type of finish and how to apply?

[Knottscott]

Wish I could help Jeff, but I don't have any anwers for you. You might try posting your dilemna at MIMF.com

Please post some pics when you get things worked out.

[downtheroad]

From your description of the fast drying and opaque appearance, it sounds like what you might have is blushing ...trapped moisture in the finish. This is a problem with lacquer in high humidity. If this is what you have, then an aerosol blush eliminator can be sprayed on the dried lacquer to soften and open the finish to allow the trapped moisture to get out. You could also mist on lacquer thinner but I think the commercial blush eliminators work better on really tough blushing problems. These are normally available from suppliers to the professional finishing/touchup industry. Use a very light mist application. If you are successful at removing the blushing then you will be OK to recoat and/or polish after it has hardened up again.

It is really best to spray lacquer, but you can brush it on if you take some precautions. I think your mistake was in not thinning it and not adding a retarder to keep the lacquer from drying too fast. You may want to read this from The Luthier's Mercantile website: "Finishing Options For Musical Instruments" http://www.lmii.com/CartTwo/FinishOverview.htm

Mohawk Finishing Products' Super Blush Retarder:
http://www.mohawk-finishing.com/cata...asp?ictNbr=451

Master's Magic's Blush Eliminator:
http://www.gemini-coatings.com/p/12628/Default.aspx

König's Moisture & Bloom Remover:
http://www.konigtouchup.com/BuyNow/m...eandbloom.html

Our shop has had really good success with the König product and it is available in 3 strengths.

[germdoc]

Tony--

Thanks for the advice. This was a first effort, and I learned quite a bit from the process. One was not to use solvent-based lacquer in the future!

I don't have a spray set-up and in any event have an aversion to spraying. I prefer processes that are more hands-on, i.e., brushing or rubbing. I love shellac for non-guitar projects for that reason.

I should have used a sealer as a first step and cut the lacquer with thinner initially, plus maybe using retardant. I think that would have prevented the problem.

For future projects I will probably go with a water-based lacquer, again brushed on.

Someday I might be persuaded to set up a sprayer...

[downtheroad]

I don't have a spray set-up and in any event have an aversion to spraying. I prefer processes that are more hands-on, i.e., brushing or rubbing. I love shellac for non-guitar projects for that reason.

I too love shellac. Being taught the classical guitar from my father, a professional player/teacher, I've had the chance to meet some very good guitar makers and play some very good instruments. Shellac is the traditional finish to use on classical guitars and all of the instruments in our family that were made before 1975 were finished with shellac applied in the French Polishing method. I have used it myself on instruments that I've restored and on antique furniture that I work on in the finishing studio that I work at. In fact, the largest piece that I have French Polished was an antique French armoire that was over 8 ft tall.

It is not an easy technique to master, but if you are interested, you should be able to find good information in books and on the internet. A friend/student of my father has put together a video on French polishing for guitar builders and is starting to import/sell different types of raw shellac flakes. You can check them out on his website here:

French Polishing DVD

Shellac for Guitarmakers

[germdoc]

Yep I'm familiar with the french rub technique though I've not used it.

I spot-treated those blotchy areas with lacquer thinner then rubbed with steel wool and recoated with lacquer. After 4-5 applications they are finally filling in and looking glossy.

I still don't understand what happened but it's been a real pain to deal with. Once everything dries and cures I'll wet sand to 1200 grit and polish.

On the positive side the guitar looks really sharp--blond wood with black binding. I'm adding a tortoise pickguard just for the heck of it (I realize that's not traditional for a classical, but I didn't put in a rosette and I need something extra for appearance. I'll take pix when it's finished.

[germdoc]

Update--

After many repeat applications I "filled in" the areas that were blotchy and dull. After drying for 2-3 days I wet sanded the entire guitar and unfortunately sanded down too much in one of those areas, I removed all the finish. So now I'm back to square 1, reapplying lacquer to that spot.

The finish on the remainder of the guitar is "OK", but I'm not real happy with it--it's not flat or glossy enough. I'm probably spoiled by having factory-made guitars that have absolutely flawless finishes you could use for shaving mirrors.

If (when) I make another classical I will probably use shellac. For a steel-string guitar I will probably go with Behlen's brush-on lacquer.