Four Part Harmony

I’ve been spending some late nights in the shop these past few days, getting started on the finishing process. It seems a bit strange to be doing the finishing when there are still unfinished pieces of the guitar, but it’s just the way it makes sense to be done I guess. It’s easier (some would say) to finish the top before the bridge is in place, so you don’t have to work around it. So I’ve carefully and accurately marked the bridge location, taped it off with masking tape, and gave the guitar it’s first sealing wash coats of shellac. I’m using an amber shellac, which is pretty dark. I was worried it might be too dark, but I actually am really liking it. It has a warmth to it.

As I mentioned before, I decided to try my hand at french polishing this guitar. It’s a traditional method of finishing all kinds of musical instruments, basically consisting of building up a thin layer of hand rubbed shellac over the entire surface of the instrument. While most production steel string guitars these days are sprayed with nitrocellulose lacquer, some high end steel string guitars and most high end classical guitars are still french polished today. I like it because the shellac is non-toxic and there are no fumes, save the small amount of alcohol that the shellac is dissolved in. This means I can pretty safely do it in the basement without fuming out our house or causing an explosion. Lacquer, by comparison, is pretty toxic stuff. The hand rubbed finish is really nice too, the trade off being you have to kind of work for it.

Here are the high tech polishing materials I am using. The primary tool of the french polisher is the “muneca”. I made mine from a few scraps of a wool sweater that Nicki had picked up at the thrift store. I also sacrificed one of my old t-shirts (the older and more worn the better apparently). The wool is used to hold the shellac and deposit it onto the surface of the guitar in very small quantities under pressure.

Prior to any application of finish, though, the most important step is in preparing the surface of the guitar by filling all of the pores in the wood. Rosewood is very porous, and if the pores aren’t filled, then I guess the shellac will just sort of sink in to them over time. The traditional way to fill pores for french polishing is with some fine pumice and alcohol. The alcohol dissolves the shellac from the wash coats and the pumice abrades fine fibers from the wood. The resulting mix of material is then gradually (very gradually) rubbed into the pores. That’s the idea anyway. I spent three consecutive evenings working at this, each night ending with a pretty sore arm and shoulder. Still, eventually I got the entire back and sides filled. Thankfully, the spruce on the top is a closed pore wood, and didn’t require filling.

Since completing the pore filling, I’ve managed to get the first “bodying” session with the shellac finished. Compared to the pore filling, this has been much easier, and much more enjoyable. There is definitely an acquired skill to it. You have to strike the right balance of shellac, alcohol, and olive oil (a drop or two as a lubricant) on the muneca to get the shellac to flow properly. Maybe I’m lucky (or maybe I’m not doing it right), but it has been going pretty smoothly.

Here’s another view of the back after the first session. In theory, I’ll do about four of these bodying sessions before switching to a lighter cut of shellac and smoothing out the finish. In between sessions, I need to let the shellac “gas off” for a day or so.

Here’s the top, which has taken on a nice amber color.

Here’s a view of the top and sides. You can start to see the reflections as the finish builds.

And here’s another view of the back, where you can really see the reflection. Hopefully I can keep the finish looking this good as I do subsequent sessions.