The French polishing process is not terribly complicated. First I create a pad by wrapping a small piece of wool with a square of cotton cloth. I soak the wool with shellac and alcohol. The proportion changes depending on where I am in the process. When starting out I use just a 3lb. cut of shellac. As I apply more coats I start using more alcohol. For the last couple of coats I only use alcohol.
After soaking the wool, I apply a small amount of mineral oil to the outside of the cloth. The oil lubricates the surface keeping it from heating up as I apply the shellac.
I rub the pad over the wood in a circular motion, being careful to glide the pad onto the surface and then gliding off. I never stop moving on the surface.
Early on, ridges will develop, don't worry. Shellac will continue to flow as it dries. With each pass the coats blend together. Increasing the alcohol helps soften the rough edges eventually creating a smooth surface.
After about every three or four coats, I flat sand with 320 grit wet/dry paper and use mineral oil to keep the sand paper clean.
For this build I spent far more time on the shellac process than I wanted. I'm still quite the novice at French polishing
Now that the surface is smooth I drop in the pickups and place the bridge to make sure everything fits, before moving on to final sanding and polishing.
For sanding I run through wet sanding with mineral oil, starting with 400 grit moving onto 800, 1000, 1500 and finally 2000 grit. I then begin the polishing process with a 4F Pumice Stone mixture. I apply with the grain, rubbing the mixture into the finish. I then wipe it off in the same manner with a clean cloth moving with the grain.
I let this cure over-night. Then I move onto a finer Rottenstone mixture. Again applying and rubbing with the grain, and wiping it off in the same manner.
This might be helpful with regards to color. If your'e going to French polish, each session you do will darken the color due to the build up of shellac. However, as you start using more alcohol, if you rub harder you will be burnishing the guitar. This is really where the color darkens, of course this is also where the you achieve a mirror like finish. So if you are looking for a satin finish, then I would stay away from French Polishing, and use an oil & urethane finish such as General finishes Arm-R-Seal.An outstanding finish without all the work.
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