Acoustic Guitar Construction

I had a nice conversation with Brian Burns the other day and he mentioned his method of filling pores that sounds very easy and effective. He mixes 1 part of 2 pound cut shellac with 2 parts acetone. The result is a .6 pound cut shellac that penetrates pores and dries extremely fast. It does all its shrinking in three days and can be recoated without worry of witness lines. He uses no oil. He levels with 1500 Micro Mesh on a rubber pad.

Open pore woods he has finished this way three years ago still show no sign of pores from further shrinking. He does not expect there will be any more shrinking in the future.

I would think Tru Oil would adhere well to such a base, as the leveling would leave the shellac only in the pores. Everything sticks to shellac anyway. You could even put a thin coat of shellac over the filled pores if you needed an even base for the oil.

This might be a way to have your cake and eat it too. Easy no hazard fill (acetone is a fire hazard but not a breathing hazard), easy no hazard finish, plus no reflective pores. I would try on a sample piece of wood first though. Brian finishes with standard French Polish, not oil.

TO adheres very well to shellac base.

Will TO just scrape off for when you want to glue the bridge on?

Yes, or as I do, you can cut the bridge shape out of a strip of tape, and put that 'mask' in the right location and then just sand off the finish. It goes very quickly and easily.

John Link wrote:I had a nice conversation with Brian Burns the other day and he mentioned his method of filling pores that sounds very easy and effective. He mixes 1 part of 2 pound cut shellac with 2 parts acetone. The result is a .6 pound cut shellac that penetrates pores and dries extremely fast. It does all its shrinking in three days and can be recoated without worry of witness lines. He uses no oil. He levels with 1500 Micro Mesh on a rubber pad.

Open pore woods he has finished this way three years ago still show no sign of pores from further shrinking. He does not expect there will be any more shrinking in the future.

I would think Tru Oil would adhere well to such a base, as the leveling would leave the shellac only in the pores. Everything sticks to shellac anyway. You could even put a thin coat of shellac over the filled pores if you needed an even base for the oil.

This might be a way to have your cake and eat it too. Easy no hazard fill (acetone is a fire hazard but not a breathing hazard), easy no hazard finish, plus no reflective pores. I would try on a sample piece of wood first though. Brian finishes with standard French Polish, not oil.

I should try this. I wonder how may coats it takes to fill the pores.

I've watched Brian do this - he pore fills and finishes a guitar in a few hours - in fact the luthier David Schramm, using Brian's method, totally pore-filled and finished a guitar in 2 hours!

Brian pads it on, back and forth, till the back is covered - maybe a minute or two - and then just starts again, maybe with figure 8's, then starts again and just keeps going until he has enough finish on it. Done. Waits a few days for any shrinkage.

Brian told me a chemist friend of his said the mix of ethanol, acetone, and the little bit of water that always comes with ethanol forms something called an "azeotrope" which evaporates faster than any of its components. Because it is so thin, it penetrates instead of skims over pores. Because what remains is pure shellac, it is clear - unlike the mix of shellac and pumice used in traditional French Polish which is a little milky. Eventually shellac cross-links as it ages and becomes insoluble. But like Dave says, shrinkage occurs rapidly, then is stable.

He gave me all this info and more while I was ordering his sharpening system. Then sent me several PDFs filling in with more details, including his whole method for French Polishing, which is quite straightforward and doable. Quite a generous fellow. It takes just 3 minutes to put a razor edge on a tool with his system, too. Also straightforward and doable.