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Tag Archives: french polishing

Another damaged soundboard

A while ago, I wrote about repairing the damaged soundboard of a cedar topped guitar. And I’ve recently had to deal with a similar problem, this time caused by the lid of the case falling on the guitar as it was being lifted out. The damage wasn’t structural but it did leave some conspicuous dents.

The soundboard had been finished by French polishing and I reckoned that simply re-polishing the damaged area would be almost enough. However, first, using a hot (but not too hot) iron and some wet kitchen paper, I steamed out the dents. When dry, I lightly sanded the area before brushing several coats of clear shellac into the places where the polish had been chipped off. After a couple of days to allow it harden, I sanded again with 1500 grit paper to level the area and then re-polished the whole of the lower part of the soundboard in the traditional way using a pad to apply the shellac. Another few days for the shellac to harden, a quick buff up with some burnishing cream and damaged area was almost invisible.

But not completely invisible because, viewed in certain lights, the repaired areas were just identifiable as slightly paler patches. You can see them in the photograph below. I had exactly the same problem with the last repair and I don’t know how to eliminate it. This time I tried exposing the bare wood to UV light for a few hours before applying any shellac but I’m very doubful that it made any difference. Maybe I should have left it under the UV light for longer. If anyone has a better idea, I’d love to hear from them.

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French polishing two guitars

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:

Finishing and polishing

I’m french polishing the guitar at the moment and this is not a process to be hurried. It’s important to let the polish have time to harden. If you don’t, and try to finish the front before the back is properly hard, it’s easy to spoil what you’ve already done. So to avoid the temptation to go too quickly, I’ve started to prepare for the next instrument. The person I’m making it for chose a nicely figured set of cocobolo, which I’ve just cleaned up to remove the sawmarks, and I’m thinking about the best way to bookmatch it. Here are the possibilities (click on the thumbnails to enlarge):

There’s a tiny flash of light coloured sap wood visible in the first and last and, if I chose either of these combinations, I’d have to make the additional decision of whether to leave it in or cut it out.

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