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    Guitar refinishing – nitro vs poly and how to remove a polyester finish

    Posted in: Mark Knopfler gear, guitar in general, misc by Ingo on January 02, 2009


    Over the last days I was working on a Strat project. I had some parts from a 70ies Japanese Strat copy, which together with an American Fender neck and a loaded pickguard should make a nice part-o-caster.

    In the seventies many guitars were finished with polyester. This finish is like a coat of hard plastic (actually it is rather a resin). It is easy to apply because you can sand it without much danger of sanding through. This was Fender’s main reason for changing from nitro to polyester in about 1968. Before, a finish that was sanded through had to go back into the production process and had to be repainted, one of the reasons why it was common to find a finish over some other colour.

    As far as sound is concerned, almost everyone agrees that a thin nitro finish that allows the body to vibrate much more than the thick plastic-like polyester  allows a better  sound with clearer treble. This might  surprise those who think that an electric guitar is  like a blog of wood and the sound depends only on the pick-ups and not on the acoustic qualities of the wood or other parts. But this is really the case, I can definitely hear how a Strat or any other solid-body guitar sounds from playing it without amplifier.

    So it makes sense to remove a polyester finish and replace it with a nitro finish. Many modern guitars are finished with polyurethane by the way, which is a bit similar to polyester but thinner so the sound is not that much affected.

    Removing polyester is tricky. The problem is that chemical paint strippers in most cases will not work. There are some types that are said to work more or less but the ones I tried did not. I solved the task twice some yeasr ago by sanding down the finish, but believe me this is nothing that you ever want to do. It takes ages to sand through such a thick plastic coat.

    This time  I tried something else, something that was recommended in a guitar forum: heat. I used a cheap heat gun and a scraper, and with these tools the finish was off in about 2.5 hours, including the control cavity. I did not heat  until the resin bubbles (which others have described) because then I could only remove rather small pieces. With less heat it was possible to move the scraper under the poly coat and to run it between the wood and the poly so that I could remove rather big pieces of the poly coat. The wood was not hurt and looked almost untouched. I can imagine that if a guitar was refinished with poly over an existing nitro finish, it might be possible to restore the original finish this way.

    All the poly chips had a weight of about 125 grams (4.4 ounces), and in the case of one of those jobs I did a few years ago it was even 200 grams (7 ounces), so the guitar becomes noticably lighter.

    removing-poly-finish-1

    After applying heat the polyester finish could be removed with a scraper

    This way the finish came off sometimes even in big pieces

    This way the finish came off sometimes even in big pieces

    The body after the job

    The body after the job

    The poly coat had a weight of about 125 grams (4.4 ounces)

    The poly coat had a weight of about 125 grams (4.4 ounces)

    This picture gives you an idea of the thickness of the polyester coat

    This picture gives you an idea of the thickness of the polyester coat

    Sound differences

    As said, there is definitely a difference, but it depends on the thickness of the poly coat, and it is still a subtle difference. The high end is clearer while the poly sounds more compressed. Some years ago I made a sound sample to document the difference between the poly finish and the bare wood so you can decide for yourself. The sound difference when playing the guitar yourself appears even bigger than on this clip. The sample was recorded with the same strings and the same setup, one time before the job, and again immediately after. What you hear are the harmonics at the 12th fret. You can click into the blue status bar to a/b compare it at different positions.

    Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

    Should I or shouldn’t I?

    The question if the amount of work and the costs are worth the increasement of sound or not cannot be answered generally. First it must be said that refinishing an original Fender – even if it is one of the least desired, heavy 70ies Strats – drastically decreases the value of the guitar! Even those Japanese vintage guitars like the first Squiers, Tokai Springy Sounds, Grecos and so on, will be worth more with the original finish, even if it is poly (the more expensive ones were sometimes nitro anyway).

    If you however have a guitar that was refinished anyway, you have not much to lose. If you are not sure if your finish is nitro or poly (polyester or polyurethane) you can find it out with the following trick: take some ordinary paint thinner and apply it to a tiny spot of the finish (e.g. under the pickguard or near the tremolo springs). If it solves the finish (paint is removed or it becomes dull) it is nitro, if not it is poly.

    I think almost all of Mark Knopfler’s guitars are nitro, at least his vintage guitars, the Schecters, the Pensas and the MK signatures are. I can’t think of one that might be poly, maybe his blue Fernandez (but maybe not), but I don’t know about some of the odd ones like his Teisco Spectrum, the Eco on “Song for Sonny Liston”, and some more. His two red Fenders from that early Dire Straits days were both refinished but these do not seem to be poly, either.

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    12 Comments »

    1. Hello
      and thanks for the article. I was wondering if such a job could also be done with guitare that have a flamed maple top and a 3 tone fender like finish. The trick with heat sounds interesting however I’m frightened that by this the finish will become a different colour or dark spots. What do you think about that. I can send you a picture of the body it is by Allparts and I really like the finish, however I don’t like that stupid plastic and real nitro bodies as you know are quite expensive
      Cheeers
      Stefan

      Comment by Stefan — 28. March 2009 @ 10:11

    2. What do you mean with afraid the finish will become darker? Didn’t you say you want to remove it anyway, or what? I made the experience that the poly coat could be removed with heat and the wood beneath it was not touched, darkened or anything.

      Comment by Ingo — 28. March 2009 @ 16:07

    3. Hello!
      Very Interesting post! Thank you for such interesting resource!
      PS: Sorry for my bad english, I’v just started to learn this language ;)
      See you!
      Your, Raiul Baztepo

      Comment by RaiulBaztepo — 29. March 2009 @ 00:19

    4. I only wanted to remove the poly not the colour and flame finish, but I guess that doesn’t work.

      Comment by Stefan — 30. March 2009 @ 17:17

    5. [...] Anyway thought it was worth putting it up for any who are looking for an alternative to sanding. Guitar refinishing – nitro vs poly and how to remove a polyester finish | Mark Knopfler Guitar / Mor… __________________ "Rock ‘n’ Roll ain’t no riddle man, To me it makes good good [...]

      Pingback by Removing Poly..... - My Les Paul Forums — 7. June 2009 @ 02:55

    6. That seems about right. Except the type of finish we are talking about is polyurethane, not polyester. I guarantee there are no guitars on this planet finished in polyester. I have polyester fleece jackets, or hats. That would not be a very resonant finish…

      Comment by Eric — 29. June 2009 @ 21:33

    7. It’s your imagination. For solidbody guitars; the electronics – more specifically, the pickups account for over 80% of the overall frequence response. This is the opinion of the majority of makers who even care to spend the time to make the boring argument. The sonic differences between lacquer and polyesters are really only discernible when describing a vibrating soundboard; and even then it isn’t readily evident to the human ear. The last comment by Eric is uninformed at best. Urethane is used primarily as base coats and filler with urethane making up the majority of build and top coats. See Warmoth.com paint technique page for more information. Polyester takes many, many forms; not just lounge lizard clothing – that was just silly.

      Comment by Gary Penton — 23. September 2009 @ 00:55

    8. Correction: Polyester for base and grain filling and then urethane for clear coats.

      Comment by Gary Penton — 23. September 2009 @ 00:57

    9. >the pickups account for over 80% of the overall frequence response.

      When I was young I thought like you and exchanged PUs in my Strat. Unfortunately this did not bring me closer to the desired sound. Pick-ups are like microphones: if you use the same mic as Mick Jagger you might have the same frequency response, but still you don’t sound like him. In the contrary, Jagger will sound like Jagger with all mics.

      It is the wood, mainly the neck, that is most important *to my experience * (and yes, I exchanged so many parts myself to come to this conclusion and do not write about what I heard somewhere)

      >>The sonic differences between lacquer and polyesters are really only discernible when describing a vibrating soundboard

      My guitar is not a vibrating soundboard and it changed its sound after removing the poly. Didn’t you listen to the sound clip ??

      Comment by Ingo — 23. September 2009 @ 06:26

    10. I’m just trying to discourage people from ruining a perfectly acceptable finish on a solidbody guitar; assuming the finish isn’t already damaged beyond repair.

      When I was young it was 1964. I build guitars for a living now that I am a retired Naval Aviator and able to do what I want. I attended the American School of Lutherie with Charles Fox when it was in Healdsburg and I graduated from Luthiers International in Atlanta. I studied Classical Guitar making with Ken Hill of Hill Classical Guitars near Santa Cruz. Of interest is that I spent my military career as a submarine hunter in the P-3C Orion. All manner of sophisticated listening devices were my tools and I was very good at it.

      The proper experiment would have been to use the same model guitars finished with the different “hard” finishes with the same pickup and settings. The frequency response will not be easily discernable but can still be measured to show that the ’sound’ (for lack of a more specific term) will be nearly identical assuming that the string gauge, string spacing and pole/string distances are the same.

      If you removed the polyurethane and didn’t refinish with any other ‘hard’ finish the difference would be audible – it would be muddy. Sound files for the internet aren’t very good indicators for anything. The sound files are necessarily low quality so if you still argue your case, I submit that you accidentally exaggerated one or several electronic settings on the guitar and/or the mixing board and/or the recording device… which will also affect the tone to a very significant degree.

      In “Cunning Stunts”; arguably the most well-produced Metallica live performance, Kirk Hammett played a clear acrylic guitar with different colors of sloshing water in the voids. Pretty telling.

      Of course, my opinion will likely fall on deaf ears (pun intended) because “we sometimes hear what we want to hear no matter what is actually heard.”

      The world is not flat and that is that.

      Comment by Gary Penton — 9. October 2009 @ 01:04

    11. I think maybe the heavy layers of signal processing between Kirk Hammett’s sloshy, acrylic guitar and the recording desk might have had significantly more effect on the sound than the water in the voids, to be honest.

      The difference is there alright – I too have tried it with an 80s Jap Strat. I’d played the same Strat for 20 years, and knew its tone as well as I know my own voice, and believe me it changed. It is quite subtle, and only really noticeable when running straight to a clean amp with no effects. But that’s what I do most of the time, so that’s good for me.

      I think the reason it is a bit of a controversial subject is that it shouldn’t really make that much difference – just like a bumble bee shouldn’t really be able to fly – but it does.

      Maybe some people are better at listening than hearing.

      Comment by jakehadlee — 21. October 2009 @ 13:04

    12. I took about two minutes to find a blog written by the Fender finishing shop. This is an excerpt but if your skull is still not penetrated with common sense I suggest you read the entire text at http://www.tdpri.com/forum/archive/index.php/t-19860.html.

      Here is what Mark Kendrick who has worked at Fender for years has to say about it: “Nitro is not a superior finish. An electric guitar doesn’t ‘breathe’ at 120 db.

      My first year at Fender I personally painted approximately 46,000 guitars. I like polyester. I like Nitro colors too. But maybe I’ll let the players that use poly (ester or urethane) speak for themselves…

      Billy Gibbons, Geddy Lee, Alex Lifeson, Joe Perry, Jimi Hendrix, Eric Clapton, Roccco Prestia, Jimmie Vaughn, Nils Lofgren, Vince Gill, Chet Atkins, Tom Hamilton, Lenny Kravitz, Merle Haggard, Don Rich, Darryl Jones, Mike Stern, Larry Carlton, Peter Frampton, Sting, Marty Stuart, just to name a few. More are available upon request. Mark Kendrick, Fender Musical Instruments.

      Comment by Gary Penton — 9. January 2010 @ 19:33

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