Learning how to French Polish
A skill that I was keen to learn while here at the Somogyi workshop was French polishing. All of Ervin’s guitars are finished in this way, because Ervin believes there are tonal benefits. We don’t do that in house, rather the guitars are sent out to Eric, a French polishing specialist. For my own guitar, I could also opt to send that to Eric, or to Adam, the lacquer finish specialist. Sending my guitar out to be finished would be a big time saver, and it is quite tempting. However, as I’m here to learn new skills, I decided I’m going to try to French polish it myself.
Before attempting it on my guitar, I wanted to figure out a process that worked for me, and practice until I was confident I could get a good result. I didn’t have much wood in my collection here to practice on, so Ervin was kind enough to let me use a set of Brazilian Rosewood that was quite thick. I’d just sand off the finish when I was done and there would still be plenty of material.
First I joined the back with a tapered centerstrip. Then I sanded it, to get it ready for the pore fill.
I decided that instead of using the traditional pumice pore fill, I'd go with epoxy as I believe it is better suited for the job. I wiped on and squeegeed off multiple coats, until the pores were filled. Then sanded all the epoxy off the surface leaving it just in the pores.
After the pore fill, I built up some shellac by wiping on multiple coats by hand.
I did a few coats, let it dry, then level sanded the surface a bit. After multiple sessions of this, I wiped on 1 final well thinned coat of shellac.
At this point it was time to rub out the finish to the final gloss. The traditional French polish method involves burnishing the surface with a cloth pad, shellac, oil, and alcohol to achieve the final polish. I opted to go with a different technique - sanding and buffing using modern abrasives. I polished only the left side, you can see the difference in the clarity of the reflections compared to the right.
This was quite a worthwhile bit of practice, to figure out my process and know that it's possible to get a decent finish using what we have in the shop. I was curious how thick the finish ended up, so I scraped a patch down to the wood and measured the step with callipers. The final thickness was .0025".