The French Polish Debate
It’s a question I get asked all the time – is French polish the best finish for guitars. The short simple answer is no. The common misconception is that french polish is the best finish acoustically especially for classical guitars. It may have been 50 years or more ago but not now. I have heard guitar builders and players claim that they can hear the difference. Sorry for the bluntness but I am sick of hearing this.
Yes, for the trained ear it is possible to hear a difference from one guitar to the next. And some may have different finishes on them. But the reason they sound different has nothing to do with what was used for a finish. It is almost impossible to say a difference in sound is solely due to the fact that someone used varnish or lacquer instead of french polish.
A french polished finish is the least durable of all the finishes. This is not practical for something that is handled so much. A French polished finish will also dull over a surprisingly short time and need a touch up. The only place I do any kind of French polishing is on the inside of the sides. The reason – shellac is a great moisture barrier and the insides are not handled.
How did this Rumor Get Started
This notion got started because French polish is a very thin and flexible finish. The way it is applied produces a very thin finish. And that finish is soft. But today all finishes are soft. One reason is that manufacturers were forced to change the composition finishing products for environmental finishes. This resulted in a softer finish that is easily damaged just like French polish. If anyone remembers how hard a lacquer finish was in the seventies will back me up on this.
Another reason some finishing products became more flexible and hence softer was that cars began to have more and more body parts made of plastic which is sometimes a rubbery plastic. Plastic has a higher coefficient of expansion than metal does. It also deforms easily but it has nothing to do what was used. So the finishes had to have a certain amount of flexibility. The auto industry drives many types of finish. The auto industry started using polyurethanes and a number of other finishes to improve the time it takes to produce a finish and they all needed to be flexible.
What Makes a Difference Acoustically?
What makes the difference for acoustics – one thing – how much finish is on the soundboard – in other words the thickness of the finish. I don’t care what you put on, if you can produce a finish that is 2 mils thick on your top it will have optimal sound regardless of what you used. Does it matter how you put it on? No, how can it. You can use a brush or spray it. The only thing that matters is how much.
I have heard a difference in my own instruments. I have tried a large array of finishes and the one thing they all have in common is if the thicker the finish the more inhibited the sound becomes. Anything more than two mils and I notice a difference. The best I can describe the difference in sound is the thicker finishes inhibit the sound a bit where it almost sounds muffled. A thin finish will allow the instrument to roar.
How to Get Finishes Thin
So how do you get these other finishes thin. That is the tricky part. The first thing is preparation. It has to be prepped really good meaning flat with no voids. Second is application. You need to get it on as thin as possible, again, without voids. After a bit you will get a sense of how much finish you have on. And lastly, if its too thick, and you can tell this when you scrape finish away for the bridge, take some more off and rebuff. It will take practice like anything else worth doing. You can practice on something else until you get it down.
I have always had a problem with purists and dogma of any kind. I realize there are a lot of builders out there that will rant and rave about the acoustical benefits of French polish. Some will go as far as to claim it makes their instruments worth more because it is French polished. To them I say live long and prosper.