Tuesday, August 31, 2010


Finishing (French Polish)

It's been a while since I updated the progress on this guitar.  I've been working on other guitars while working on the the pore filling and finishing of this guitar.   

First, a little background.  Most hardwoods have open pores (open voids in the grain) that need to be filled with something in order to achieve a level surface, and a smooth final finish.  This particular guitar is Madagascar rosewood (Dalbergia Baronii) which has long, deep canyon-like pores.  There are numerous ways to fill pores, but it is usually time consuming, messy, and the least fun part in the guitar making process.  (It should be pointed out that pore filling is optional, but generally expected.)  Many guitar makers now use an epoxy finishing resin to fill pores, which has many advantages: it is clear, so it takes on the color of the wood it's filling, it enhances the contrast and depth of the wood grain, and, compared to most other methods it's easy to use (although it can be toxic to those who have a sensitivity to epoxy, which can pop up at any time). 

For this guitar, I decided to use an old, traditional method of filling: pumice (ground volcanic dust).  A pumice and French polish finish uses minimal materials, no chemicals or toxic substances, and when done well creates a beautiful, organic looking finish.  It is also very labor intensive.  Filling the cavernous pores of this wood with pumice has turned out to be a journey in itself, involving a lot of backtracking, research and trial & error.  As the pictures show, the back and neck of the guitar have been filled and French polished (a method of applying shellac by rubbing it on in micro-thin layers with a pad).  I'm still working on filling the sides of the guitar.  Thank goodness the top (spruce) is not an open pore wood and doesn't need to be filled.

Filling the pores involves rubbing pumice into the wood using a pad, alcohol and a bit of shellac.  The details of the process differ with each practitioner, and the scant literature on the subject is rife with contradiction.  As previously mentioned, a lot of trial & error was involved.











The next post will show a mostly completed guitar, with a little more detail about French polishing.