Guitar Finishes

      It's hard to tell, it's hard to tell, when all your love's in vain. May 17, 2005

Question
Could someone set me straight? I'm bombarded with confusing info on guitar finishes. Nitrocellulose, waterbased lacquer, oil, polyester... It seems people are using everything. What's best, and why? And exactly what is a polyester finish?

Forum Responses
(Finishing Forum)
From contributor W:
First of all, there are many different options for finishing guitars. This is for a good reason. Every different coating family represents something unique to its application. Basically, all of the above are used, and more. What final look are you seeking? Each of the different finishes or families gives a completely different look. Most people, when finishing guitars, want the look of glass. The best way to achieve this is by using polyester. A polyester has very high solids (generally 85% plus). It also has very high filling properties as well as great resistance to sagging. But the reason for using it is it gives the look of plastic. The transparency is superior to anything else. Polyester is a sanding sealer, and is used as only part of the overall finish system. The system as it is would consist of a polyurethane insulator (1 coat), a polyester sanding sealer (2 coats), and finally a polyurethane topcoat (1-2 coats).



From the original questioner:
Is one finish preferable over another for tonal quality?


From contributor B:
Nylon string guitars are very sensitive to hardness of finish. French polished shellac, which is a very thin (2 mil or so) and hard finish is definitely the best for them on the soundboard, in my opinion. The back and sides can be finished with most anything, preferably something tougher than shellac.

I much prefer the "natural" look of shellac, but that's because the great old Spanish guitars were finished with it, and I associate it with quality. Having said that, an excellent classic builder, Robert Ruck, uses a modern finish everywhere. I'm not sure which, but one of the finishes mentioned above.

Until a year or so ago I would have said that steel string acoustics could be finished with most anything, but Ervin Somogyi, arguably one of the very best SS builders, now French polishes his soundboards, and says they sound better. He does the backs and sides in nitrocellulose lacquer. So I'm sticking to shellac for the soundboards of my Classics and Flamencos, but still looking for a tougher finish for the backs and sides.



From contributor J:
What type of woods are you planning on using for your instrument? The finish you desire is based on the acoustics specific to its style and function. I think the only thing that luthiers or finishers can agree upon is that sound is optimized best on unfinished wood instruments made with the proper density woods. Then you start getting into the characteristics that finishes will bring or not bring to the table for specific use requirements. If I was to take the best of all technology and was only given one finish I could use for everything, I would go with a tung oil and after a couple applications, finish it off with a wax emulsion mix to add other properties.


From contributor R:
Are you making acoustic or electric guitars?


From the original questioner:
It's an acoustic guitar. Soundboard is sitka spruce. Back, sides and neck are maple.


From contributor B:
An oil finish might work okay on a steel string acoustic, but I killed the treble on three classics with an oil varnish before going back to shellac.


From contributor J:
Oil and varnish is a totally different animal than tung oil and wax rub out. Here's my basic knowledge on acoustics for instruments. Electric-aesthetic only. Acoustic stringed: High wearability for the necks, not as critical acoustic values for sides of instruments, fronts/backs (and I would include sides just in case). The finish should allow vibration off wooden insides to echo or the vibrations to be elongated and not deadened. This requires the finish to be hard and resilient, mimicking the wood's tones as much as possible.

I can't recall the article I read on the scientific testing on Stradivarius violin finish formula. I understood it to be shellac (very high quality from a specific region) and the one ingredient that separated this finish from the rest was the addition of some form of glass, whether silica or similar mineral. Remember that hide glue is so varied in make and preparation that this long forgotten furniture making product could also have been an important ingredient for acoustical reverb. The only drawback of shellac is its lack of wearability, but someone playing classical music isn't jumping into the mosh pit either. This finish didn't come into its own overnight - it took years to harden and be treated with waxes and hand oils, etc. to develop its unique properties. Research on lifestyle, solvent use and trends in this era is the only way to get the information I think you want to know.



From contributor D:
I know a luthier who makes acoustic and hollow body jazz guitars. He has been using 2k urethane for years. His guitars sell for thousands of dollars. The playability of his guitars and the tonal quality of his guitars are outstanding.

Martin guitars have been finished with notrocellulose lacquer and also polyester for quite a few years. Is there anything more beautiful than Keith Richards and Mick Taylor's Gibson Hummingbird acoustic guitars that you hear on "Wild Horses" and "Angie"? They are finished with nitrocellulose lacquer.

No offense, but the place for you to start your inquiries is Bob Flexner's book "Understanding Wood Finishing." By the way, Jeff Jewett, the author and finish supplier and furniture technician and everything else, is a luthier. He's a good one. He is also good at wearing all those other hats (one at a time).

I am not a luthier. I am a wood finisher and furniture technician. I am also the owner of two Les Pauls. My ears are golden (I use Ampeg amps so listen and drool). The guitars have an ordinary nitrocellulose lacquer on them.

I would not fret so much over the finish. The choice of woods is most important and so is the construction/design. Judging by the Martin standards, the finish is there to protect the wood and keep grime from working its way into the grain. Other than that, if you have good woods and good designs, you will get rich and golden tones from your projects.



From contributor J:
I have to disagree with the statement that the finish isn't all that important. It is almost as important as the design, craftsmanship and choice of woods and how they are dried. A poor finish such as a linseed oil or a thick heavy varnish is going to deaden the acoustic values by removing the resonance that the wood brings to the ear. One thing is for sure - it will be a cold day in the finish room when a polyester finish makes it into an orchestra's elite player's hands. Let's not forget that the NC lacquers that are used on high-end instruments are not the ones that we are familiar with - they are special formulas.


From contributor E:
I wonder what type of high tech finishing process Stradivarius used on his violins? Rumour has it he made some pretty good sounding ones.

As a side note, I read somewhere once that they used some unnamed chemical to treat the wood to prevent damage from worm infestations and the chemicals caused a reaction in the wood that changed its tonal quality, resulting in arguably the best sound ever produced by an instrument.



From contributor J:
I wonder if anybody would be interested in knowing the ingredients and the application methods done on the Stradivarius violins? Unless you learn how to put together varnish and colors and minerals to make your own lacquers, you will always be stuck at the mercy of the manufacturers adding fillers and extenders to keep their heads above water in the marketplace. There used to be a time when the job of apprentice was harvesting natural ingredients to mix up the journeyman's formula.


From the original questioner:
Thanks for all the input. Someone told me that the reason lacquer is chosen by some over polyester is the ease of repair. In the event an instrument is damaged and spot repairs are needed, lacquer can be touched up - where the entire polyester surface is more likely to need sanding down to the wood and an entire new coat reapplied. Yes/no?

And, I will pick up Bob Flexnor's book. Have read him for years in Woodshop News.



From contributor J:
Yes, with polyester and touchup, you have to dot your I's and cross your T's and be thorough each and every step during the repair work. It will age you quick.


From contributor D:
We are not talking about violins or orchestra instruments. We are talking guitars. The finish will not deaden the woods as much as bad design or wrong bridge, end nut or old strings will. Brightness in sound is not everything. But one thing is for sure, a cardboard sounding guitar is not worth very much.

In that I never consider any finish which is not film-forming, I would never recommend oil finishes. Varnish, shellac, lacquer, polyester, 2k urethane, autobody paint, etc is what I recommend. The proof is in the pudding. I mentioned a luthier who is local to me. He uses Dupont autoclears. His guitars fetch thousands and are worth every penny. I have played them and my ears are golden.

I have played the Martin polyester and nitrocellulose lacquer guitars. It is the guitar in hand and all that makes up that guitar which matters, including the finish. But the finish is just a minor consideration.

A good design which takes advantage of the physical properties of the guitar as well as the use of certain materials for the bridge, end nut and even the tuning pegs is unlikely to be killed by one film-forming finish or another. And if you are talking about electric guitars, the differences become even less important. The Ampeg Dan Armstrong is made of acrylic. It sounds great. The Travis Beams were made of some metal alloy and a graphite neck and those guitars were popular for a while. I prefer nitrocellose lacquer because, as one participant said, it is easy to touch up.

As for classical guitars, I have no idea what the accepted sound is. Classical guitarists are note-oriented. They are not intent on getting off on a fading out note listening to its lingering harmonics the way that us Mick Taylor fans are.

Now, just to be cynical, does it really matter? The two more popular guitar players ever, Jimmy Page and Eric Clapton, have and have had access to the most divine vintage instruments. Yet they somehow manage to wreak out of them tones that are no better than Randy Bachman on a bad day. Why? The part of the playing equation you never read in any technical forum is the part that comes from the interaction between the fingertip and the string. That magic is unique to each player and that's a tonal difference that you cannot buy in a store or dial in on your amp.



From contributor M:
I am finishing electric guitars for a guy. Yes, his basic guitars will start over $2,000. And he will tell you that finish is very important. Even the film thickness matters. That is why we are using Nitrocellulose Dope. It is the highest quality NC out there. To give you an idea of how critical his ears are, he is playing a guitar with his components without finish. The finished guitars will be compared to this one. For most of the real world, finish may not play that big of a role. But to some, it is essential.


From contributor J:
I think we can put away electric guitars 'cause they're not relying on acoustic value. I could not play the guitar if my life depended on it. But if you put on a plastic finish or one that impairs the ability of the wood's sound board to vibrate, what you have is no better than if you had made your guitar out of paint grade poplar. I understand what you're trying to say, but you bring to the table facts based on who plays whose guitar or how much money was paid for their instruments. Neither matters to me, especially the money. To say the rock style play requires the same quality guitar or music ear is out the door as well. I once heard someone say "music isn't the notes that are played, it's the silence in between the notes that make the music." It not only is the amount of finish or lack of a finish build that can ruin acoustics on an instrument, but anything even as important as where the tree grew in soil and environmental conditions. It was said that Stradivarius had calluses on his knuckles because he would travel all around and knock on the trees to listen for density. You don't think he just threw on any finish after that kind of trouble, do you?


From contributor O:
I just underwent the process of creating an electric guitar. Boy, did I learn a thing or two. Like… it's best to cut cavities before gluing the top and back together - makes it easier. Second... use stain much, much darker than the color you want or you'll be disappointed. Third... bubinga and maple don't really make a very good guitar. It sort of sounds like a cross between Angus Young and Black Crowes. Muffled lows, and piercing highs. Wish I could get them to even out.

Anyway, I used an oil based stain on the bare wood. It had been sanded a lot, probably too much, cuz it really wouldn't take the stain (why I say use a darker color and make several applications). Then I brushed on a sandable lacquer sealer. After sanding it looks really nice, and really not shiny (well, if you turn it and look across it, it has a reflection, but no glow yet). Then we used a polyurethane lacquer. I tried to spray it on, but was too stupid to realize I needed to thin it first (it never dried).

Then I screwed up and scraped the area between the two pickups, trying to drill a passage for the leads... doh! That, and the bubinga is so damn hard, I sheared off two strap peg screws in the bottom. It's all done with a crappy Gibson size neck, on a Fender size bridge... but it plays. I think the wood is the most important feature of how a guitar (electric, mind you) will wind up sounding. I suppose if you soak your wood in finish, it could muddy up the sound, but, hey - some people are looking for that. I almost wish I could muddy up mine - it's a bit too bright for me.



From contributor A:
Polyester finishes on guitars get a bad rap because of the way they're often applied. The material itself is actually superior, but slathering any finish on an eighth of an inch thick isn't going to do a guitar's sound any good at all, no matter what the material is. Historically, polyester has often been applied very thickly to save quality labor on surface preparation.

Original Fenders from the 1950's which were finished in nitrocellulose were sealed first with fullerplaste, a polyester type wood filler. Funny their original "nitro" finishes are touted as great for tone, given the fact that underneath the lacquer, there's… polyester. You have to seal off the grain with something that doesn't shrink, especially on open grained woods like ash. Polyester is perfect for the task. You can apply nitro lacquer over polyester, but you can not do the reverse.

By the way, lacquer is a very misleading term. The term derives from the lac insect, and indeed, a finish is made from it: shellac. Lacquer doesn't contain any lac whatsoever. Go figure. Nitrocellulose is made from nitrated cotton fibers; it starts out as the main ingredient in smokeless gun powder before it becomes a finish. I digress...

The next finish used on guitars was acrylic lacquer. Acrylic lacquer and nitrocellulose are only compatible one way: You can put acrylic lacquer over nitro, but you can't put nitro over acrylic; it will instantly check, wrinkle, and do all kinds of ugly things. My experience with acrylic lacquer is that it does not have the depth of color or gloss that nitrocellulose lacquer has, it scratches more easily, and is just as sensitive to chemicals and contact with other plastics. I don't believe it was introduced because it was better than nitro, I believe it was developed because it was cheaper, had better color retention in outdoor applications, and was less flammable. Sometimes it's the only sensible choice though, especially when doing custom finish work such as candy apple 3 stage finishes. Nitrocellulose tends to yellow with age. That can be very desirable over wood, lending a warmth of color. But it doesn't look too good on bright colors or metallics you want to retain their brilliance. So it depends on the color too, which finish offers the best performance and appearance, all things considered.

Finally, there is polyurethane. I consider it the least desirable finish to use on a guitar for tone and appearance; it's very "rubbery," it surface scratches quite easily, it has a *slightly* hazy appearance even after the best polishing (best noticed under fluorescent lighting) , and even after wet sanding and buffing, a slight texture tends to redevelop after several days (due to its ongoing affinity for continued cross linking). Like polyesters, most polyurethanes are catalyzed with a hardener.

Polyurethane is what 99.9% of auto body shops use today for repairs and repaints. The only thing it has going for it, in my opinion, is that its flexibility renders it pretty tough against stone chipping and automatic car washes, a major problem with the front end of an automobile. It stands up well to harsh sunlight, and hail too. Not too much of a problem for most guitar players.

But that same flexibility is at the expense of its capacity to take a good shine with a buffer, and in the case of a guitar, to not kill the tone. A harder finish is better for anything that needs to resonate (like a guitar).



The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor G:
On a solid body, strings are anchored by a metal bridge on one end, and a plastic or composite nut on the other. The magnetic pickups detect the string vibrations and send signal to the output. So, type of wood has absolutely nothing to do with the sound of your electric. A better design (neck-thru) can give you a little more sustain because there is no joint to absorb energy. But as far as tonal quality the only thing that matters is the electronics.



Comment from contributor S:
I agree and disagree with many of the statements. Finishes on an electric guitar are as important to sound as with any other instrument, especially if the musician specializes in that instrument. I have been creating "art guitars" recently and done a lot or research on the subject. A review I read of early PRS guitars compared to new PRS guitars, in terms of sound was shocking. The differences? Nitrocellulose vs. polyurethane/polyester. The former having amazing tonal qualities that the latter can't provide. Granted, the thickness, more than likely, has a lot to do with that. Manufacturers are using Poly and applying it thickly to save time and money in finishing and have the smoothest/glossiest finish. (Good musicians can tell the difference in the sound instantly).

My first guitar I used polyurethane and ended up fairly nice, however after blocking, polishing and buffing the finish continued to decline as all the swirls and imperfections slowly started to come to the surface (months later). That's when I researched and started using Nitro. It has all the qualities that I was looking for. Applies easily, sands and buffs wonderfully (although it can burn with power sand/buffing if not careful), and the sound is much cleaner. Nitro can be very soft during the curing process, however it also has the wonderful quality of being very easy to spot repair.



Comment from contributor L:
"On a solid body, strings are anchored by a metal bridge on one end, and a plastic or composite nut on the other. The magnetic pickups detect the string vibrations and send signal to the output. So, the type of wood has absolutely nothing to do with the sound of your electric. A better design (neck-thru) can give you a little more sustain because there is no joint to absorb energy. But as far as tonal quality the only thing that matters is the electronics."

The above statement is partly true, but how the strings vibrate also depends on the things such as wood type, neck construction and etc. You have to think of it as a whole system. For instance if the strings were attached to a huge diamond (a very rigid crystal structure) the string's vibration would still be affected by it. On the opposite end the guitar would be made of a less-rigid material, like rubber. In any case, materials exhibit different responses when excited at different frequencies (modes). This is well known to acoustics engineers and civil engineers.



Comment from contributor A:
I sell guitars for a living and have for the last eight years. I'm a guitarist of 22 years now as well. I handle and play literally thousands of guitars a year. They are my passion and joy.

Finishes have a huge impact on the tone of a guitar, whether it's acoustic or electric. I really can't overstate this. I wouldn't necessarily say finish is a bigger factor than choice of wood, but I have definitely heard some very well built guitars turned to paperweights by a polyurethane or polyester finish that's simply too thick. Nitro sounds best. It really does. It tends to age with the instrument as well, giving the guitar a "broken in" or "more open" sound.

Thin polyester is, in my opinion, the next most musical choice - the thinner the better. Even with electric solidbody guitars the thicker the finish the more it damps the resonance of the instrument not only in the upper registers but through the entire frequency range. Acoustic guitars show an even more pronounced difference in tone with different finishes. Nitro covered instruments such as Gibson’s or more expensive Martin’s are louder and brighter, but also much richer in the low and midrange frequencies. They'll mature much more quickly and much more beautifully. You really don't find many French polished guitars, but I know a very talented luthier that will use a French polish for the right price (10k or more usually). I really can't say that French polish sounds better than a nitro finish and from what I understand it's extremely difficult to apply.

The trade off for real tone is durability. Nitro, when applied correctly, is very thin and will eventually begin to sink into the instrument allowing the grain of the wood to show. Most guitarists like that though. I would never recommend a poly-anything over nitro for tone.

Paul Reed Smith and Taylor guitars are both legends in the industry for their poly finishes. Both are very quick to apply, very durable, and very easy to repair. But both makers offer very high end models that are nitro finished in the interest of a more open tone. Paul Reed Smith talks quite a bit about wood and finish and tone.

Nitro really is the king. Check out an epiphone Les Paul next to a Gibson. Don't plug them in. Just play them acoustically. You'll marvel at the difference in sound and the remarkable resonance you feel when you play the Gibson. The first time I played a Gibson 1959 reissue I could tell it was out of tune without it plugged in by the vibrations I felt through the back of the neck. Hide glue and nitro all the way.

Finish counts, for sure. It makes a huge difference.



Comment from contributor F:
The truth is I had the distinct pleasure of working as the electronics technician for an independent, but very accomplished, custom electric guitar builder for 14 years. I have seen my friend and luthier construct the most amazing electric and semi-hollow body creations one could ever hope for with my own eyes, and had the privilege of wiring almost all of the 213-or-so units that were custom built for some very particular, prominent and famous clients.

With regards to the final body's finish affecting the final tone; I agree with any comment indicating that it's really the acoustic-based instruments (a semi-hollowbody that is electrified) that would benefit from the tone offerings between densities of a Polyurethane to Nitrocellulose Lacquer. Can't argue there at all - pure physics - it matters! The resonance of an acoustic sound board obviously is affected by the density of the finish. It's not rocket science on this point. Resonance-damping materials come in all forms, and a high-weight finish is one of them! Heavy finishes kills the acoustic vibrations. Got it!

Also, with regard to any previous comment about solid-body electric guitars having not much affecting them but the neck joint - I totally agree!

We did a serious test with six accomplished guitarists, listening to our base models builds only through a blind scrim with each guitar played by the same gentleman (a famous guy too). The shapes and electronics of each guitar were absolutely identical. The only difference between them was the body's primary wood (basswood/mahogany/maple/Australian lacewood) and the finishes (unfinished/clear lacquer/polyurethane paint).

The results you ask? Well you guessed it, absolutely nobody could tell the difference in any of the guitar's amplified tone and that included the luthier and myself on top of the six test subjects.

We played them from behind an opaque scrim for two hours and no one could guess which was which. Get it? No one could identify which guitar was being played. Did we ever learn a valuable lesson that day! You should as well.

Now, to the favor of some discriminating ears there that day, a few picked up that the Australian Lacewood base model had tad more sustain (a very high density wood, thus an understandable observation), but that's it.

The case for this topic of conversation was resolved and closed for me back in 1996. It was proven to me with my own ears by others hands. I hope my comments will be taken seriously and used as a knowledgeable reference for this ongoing debate over finishes affecting electric solid-body tone.

My final word: Solid-body electrics guitars do not benefit from various finishes. It is the electronics and pickups that make the primary difference between two or more identical guitars' sound. My kind regards to all who have participated in the wonderful discussion. All the best to you and keep your comments coming!



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