A few weeks ago, I started French polishing a cedar-topped guitar and, to avoid the temptation of rushing to get it finished, I began making another to give myself something to do while waiting for the polish to dry and harden. Absurdly, the strategy worked too well; I became so absorbed in making the second instrument that I didn’t pay enough attention to the one I was supposed to be polishing. This meant that I didn’t notice a problem: the shellac that I was putting on wasn’t hardening properly.
It took me a while both to identify the problem and to come up with a diagnosis. I’d been using light mineral oil on the pad (instead of the usual linseed oil) to stop any sticking as the polish was rubbed on and I reckon that some of this oil had got incorporated into the finish and slowed up the hardening. The advice to use mineral oil comes from the chapter on shellac in Bob Flexner’s book Understanding Wood Finishing, which is otherwise a mine of good sense. It’s possible of course, that I’m wrong in laying the blame at his door but when I eventually bit the bullet, wiped off the non-hardening shellac and started all over again using linseed oil, the problem didn’t recur. I’d be most interested to know if anyone else has had the same experience. Sometime I must make some experiments with different oils to find out whether this is the correct explanation.
All of this inevitably slowed down completion of both instruments and there hasn’t been much to photograph or write about, which is why there haven’t been any posts for the last couple of weeks. Anyway, I’m now at the final stages. Here’s the current state of the two guitars:
Finely Strung 