Here you have my workshop when French polishing. I´ve been asked many times to explain how to French polish. Its something that I find close to impossible to explain. French polishing is a very intuitive and organic process and as a such its close to impossible to write it down. The different tutorials that you can find are so bad in opinion, that they are hardly worth reading.
What I´ll do, is to throw in some few thoughts of mine.
I´ll start with the photo. You see from the left:
A piece of cloth, that is where I´ll put my pad. A plate with pumice and vaseline oil. In front of this a 400 grit sandpaper (later in the process it´ll be 800 grit and 2400 micromesh) A plastic bottle with Shellack, a bottle with 96% alcohol and behind that a glass where I keep my pads so that they dont dry out.
There are some basic proceses:
*sealing the wood with a thin layer of shellack.
*On top of that you start the porefilling. You only use alcohol on the pad. Take your time, dont use to much pumice and not to much alcohol either. The idea is to dillute the shellack already on the wood and make a smeary mess that hopefully ends in the pores of the wood. Let it dry and sand it . Continue the process until more or less happy. (Although I must admit that its difficult to be happy when porefilling). Give it a layer of shellack, let it dry and take a look. Most probably you´ll find out that there werent any reason to be happy..... So more pumice, more alcohol etc.
When you´ve reached the point where you are depressed, stop porefilling, give it all a layer extra of shellack, let it dry for a day and sand it quite heavily. You need to have a more or less level surface. Now go on to next step which is building a body of shellack. Small imperfections will be filled with shellack and you can always add a little bit of pumice to that darn pore or two that wasnt filled. Porefilling can be done all the way up to the final layers.
* Building up body: Well this where its real French polishing. There are many ways of doing that. But here are a few basic concepts. The idea is to add a layer of shellack that is thick enough to be sanded level before the final layers of shellack. The pad can be loaded on the top or or from the back, inside the pad itself. It depends on you and the pad you´re using. The oil is very important and so is the thichkness of the shellack. This you have to try yourself and find what works for you.
Only use circular movements eights or circles, never stop on the surface and never do sharp turns. They always leave a signal. When not doing round movements, land and take of the surface as if it was an aeroplane. As light as possible. In general, try to add as little as possible and press very little, especially in the start of a session and press a little bit more when the pad is getting dryer. Finish every session adding a few drops of alcohol to your pad and do long strokes with the grain using the aeroplane tecnique.
* Leave to dry some days. Then sand flat with a relatively fine paper. I scruff sand very lightly with 400, sand with 800 and I finish off with 0000 steel wool, but you can use micromesh as well.
* Final layers: Thin the shellack and do mostly long straight aeroplane landings and takeoffs. The idea is to make a thin layer, as perfect as possible, of shellack. Use very little shellack and oil, dont try to cover it all in one go. Its better to do a few short sessions and let dry for half an hour in between. In practice, on a guitar body that means doing all 4 sides, play a tune on your favorite instrumen or pet your favorite animal, then go back and do all 4 sides etc. When its all covered, then sing a song or dance because thats it...
* Well, it used to be "Thats it" BUT in these days of stupid perfection, we the professionals have to leave the surfaces as close to glossy glass as possible. So here we go again. Sand with 2000 grit or finer or use micro mesh. Dont take to much off and pray to your local or favorite devine that you are not going to take to much of because then you have to go back to the final polishing state.........
* Polish the guitar with a car polish without silicone or a vinyl sealer. And be proud. Thats important. You have entered the world of mysterious old fashion ways of doing things.