Is French Polish the Best Finish for Guitars

French polishing inside of guitar sides

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.

In Closing

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.

Blog Comments

John,

Do you still use epoxy for pore fill when using Violin Varnish? And , if so, do you sand the epoxy back to bare wood or just level it?

Yes, I still use epoxy for pore filling. By sanding back to bare wood you just expose more pores. The idea is to coat and flatten. It may take two applications.

Something to think about also is your own health. Ive sprayed nitro lacqure all my life,i love it ,it melts into itself repairs easily.nitro sunbursts are awesome.but if you dont have a good spray booth,spraying nitro or any finish could cause skin sensitivity,or other worse health issues.none of us are impervious.So after a not so good doctors visit i started looking for alternatives. I used to sell behlen mohawk products and violin varnish is awesome as John says.
Ive also tried royal lac from shellacfinishes.com.i have nothing to do with them just like their product line. Its a shellac hybrid that infuses a type of poly,and makes it harder and more resistant to dirt wear and sweat.it applys exactly like shellac. My latest archtop came out great with it,and im getting more for my next builds.Best thing,i stowed my hvlp spray rig,and makeshift booth,and gave my behlen and lacqures to a guy that has a proper booth.now ive got a few more square feet in the shop for awesome woods.

I couldn’t agree more. I think this is an opinion shared by many that have been either cabinet making or furniture making for a long time. You develop a different aesthetic. I haven’t sprayed for years now. I developed a sensitivity to the chemicals and it would make me ill. People think spraying is faster and easier but they are dead wrong. Way more stuff can go wrong with spraying. Things you don’t have much control over. I now use violin varnish which is basically shellac with additives that make it harder, dry faster and a higher solids content making it a thicker finish, much like the stuff you are using. I also use an oil/urethane on the necks. They are not as slippery and look way better. I apply everything with a brush or pad. I really don’t like high gloss finishes. A nicely done satin finish has a way more elegant look for my taste.

John, In your August blog on re-doing your shop you mention that you no longer spray finishes thereby freeing up space for your office. How are you currently applying finish? Violin varnish with a brush as mentioned above?

Yes, thats right. Violin varnish with a brush and oil/urethane with a brush. The oil/urethane is great for the neck. Its satin finish so its not slippery.

Another finish related question. Generally woodworkers would always try to treat both sides of a piece of wood equally, for stability, yet the custom with guitars is to leave the inside unfinished. Especially on such a thin material as the guitar back or top is this not asking for problems as we are inhibiting moisture movement one side of the panel but not on the other? Has anyone ever tested out the acoustic effect of finishing both the inside and outside?

You are spot on about treating both sides of the wood equally for stability. Yes, putting shellac on both faces of a piece of wood greatly reduces the amount of moisture exchange, hence making the piece more stable. Laminating takes things a step further.
I once asked a well known guitar repair person what was the cause of most of the problems he saw with instruments needing repair. Without hesitation he replied “poor woodworking”. The truth is most guitar builders have very little woodworking experience other than guitar building. And many have learned from other guitar builders that had no woodworking background as well. Building a jewelry box for your mother, wife or girlfriend is not the same as woodworking professionally. In a professional environment you learn very valuable things since repair and failure are grounds for firing.
I have always put shellac on the inside of the guitar where possible and apply at least a couple of coats of shellac on the outside as well for those reasons. I have never noticed any change in acoustics by finishing on the inside. Although I have noticed a positive difference with laminating.
I highly recommend putting shellac on the inside and out where ever possible. It does help with stability and it looks nice when you peak in through the sound hole.

Hi John,

I just recently bought your book, and you only recommend to seal with shellac the sides, heel and back braces, and mostly because aesthetics reasons. However, if I understood correctly, a “good woodworking” would mean that we also need to shellac the back and soundboard on the inside?

Thanks in advance for your reply.

Shellac is a good moisture barrier and for that reason I shellac the inside of the soundboard. It reduces the moisture exchange between the wood and environment whereby adding some stability. The sides of my guitars are laminated making them very stable, therefore coating them with shellac them is not necessary but I do it for aesthetic reasons. The heel is also a stack of laminated wood and I shellac it for the same reason because it looks nice through the sound hole. The back braces and center patch are small in size and situated such that their expansion is negligible. I shellac them as well because it looks good. Putting shellac on the back would be great for reducing moisture exchange but it must be done after the back is glued on. Trying to add shellac through the sound hole will result in a mess. That is why it is almost never done.

Yes, I’m glad someone finally made this statement. The classical guitar building world is a strange place, even those who are willing to accept radical departures from tradition with bracing (lattice) and use nomex double top construction and balsa wood, with carbon fiber bracing still insist on french polish as a factor of producing “the best” classical guitars. It is a complex issue though. Balancing ease of application, durability, appearance, ease of repair/refurbishing, environmental impacts. Ultra violet light cured super finish may be an option if you are making several guitars a week (or several per day/hour in some cases) but for us amateurs working in the basement or garage it’s a different story.

The classical guitar building world IS strange indeed. Its a perception thing. People hear that the instrument is french polished and think it is better and worth more money. That is perpetuated by the builders themselves for higher profit.
To my knowledge there are no classical guitar builders making several guitars a week. And that is why you don’t see a lot of UV and other fancy finishes. They simply don’t have the volume to justify the expense of the equipment.

There are a couple of finishes that can be applied without spray equipment that in my opinion are better than French polish. Behlen’s violin varnish is one that you can apply with a brush. It has a high solids content, dries pretty fast, and buffs out nice. Its basically a shellac with some additives such as sandarac and mastic which make it harder. I used to mix a similar finish myself years ago. Varnishes like Pratt & Lambert #38 can be brushed on as well, has a high solids content and produces a very nice durable finish. I have used both with success.

As for damage over time – its a matter of degree. If its just a touch up yes, a french polish is relatively easy to restore. But if the surface of the finish has been penetrated to the wood a touch up won’t do and that will be a more difficult restoration regardless of what kind of finish is on the guitar.

There are always considerations when it comes to finish and there is no perfect finish. They all have pluses and minuses. The biggest plus for French polish is the fact that it is easy to touch up. But the fact that it usually needs a touch up after a relatively short period of time is a negative, and its something you don’t typically see with other types of finishes. Finishes that use hardeners or catalysts are typically difficult to repair because as you say subsequent coatings don’t necessarily melt into the previous ones. Oils typically use a hardener or catalyst so they usually don’t blend well into previous coatings.

Bottom line is you need to choose a finish that you are comfortable doing and one that meets all your criteria. The criteria will be different for different people. For example cure time is a criteria that pros have to seriously consider since adding ten days to a finish job is putting off your payday. Finish repair is another, if you are the one that will be doing that as well. So its different strokes for different folks.

The problem I have with people that champion French polish as the superior finish for a classical guitar is that they think it is the only acceptable finish acoustically – and that is simply not so. This is further supported by the mistaken perception that the instrument is somehow worth more if it is French polished, and that is just nonsense.

Disregarding the possible sound effects… What about fixing the finish (years) later when the guitar was used. From my experience of view every guitar gets damaged over time so I would think that from this point of view either shellac or oil would be good. Shellac bonds to itself other finishes do not so this could be a good option. What do you think?

I’m doing French Polish simply because I don’t have the $$$ to buy the necessary spray equipment, not to mention set-up a proper spray booth with proper ventilation. French Polish is an easy finish, from a start up cost standpoint, minimal materials, no fumes etc. The difficulty lies in mastering the technique itself. And while I agree it may not be superior, I think if done correctly, can certainly be as good as varnish. Any finish will deteriorate after time, lacquer, varnish, french polish, you name it. Even a Piano with a polyurethane finish can develop cracks and surface anomalies.

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