Hardness of nitrocellulose finish

Discussion in 'Finely Finished' started by Slippery Jack, Sep 26, 2020.

  1. Slippery Jack

    Slippery Jack Tele-Meister

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    I've just finished my re-spray and it looks great. I'm wondering how long it takes for the nitrocellulose to harden to the point where small dings won't leave a mark on the finish. I've got a 1984 Tokai strat with nitrocellulose finish and the finish is hard and doesn't easily mark. Will I have to wait 35 years for my telecaster to be really hard?
     
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  2. Goldenshellback

    Goldenshellback Tele-Meister

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    Nitro is what was used in the automobile business for many years. It gasses off for years but it will harden within several weeks. Apply thin coats. At least 10 coats.
     
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  3. netgear69

    netgear69 Tele-Afflicted

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    Nitro cures pretty fast but unlike poly it chips easy and cracks with extreme temp shifts
    Did you or someone refinish your tokai with nitro i would be surprised if a Tokai had a nitro factory finish
     
  4. SC Relics Guitars

    SC Relics Guitars TDPRI Member

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    I’ve just stripped and refinished an early 80s tokai and it was thick urethane. I don’t think yours is nitro. Most likely urethane or polyester.

    Nitro also doesn’t cure, it dries. Leave it for 4-6 weeks if possible. It’ll never properly harden, really. Although when it does toughen up it’ll then be prone to chipping, indentations and craze checking.
     
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  5. Slippery Jack

    Slippery Jack Tele-Meister

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    Someone told me the Tokai was a nitrocellulose finish. I bought it new. Perhaps it's not nitrocellulose, then. I'll investigate further.
     
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  6. Boreas

    Boreas Tele-Afflicted Silver Supporter

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    Take a Q-tip soaked in a little acetone (fingernail polish remover) and try it in an inconspicuous spot. Nitro will dissolve - poly won't.
     
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  7. Henley

    Henley Tele-Meister

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    Just test it...in my limited experience with Ibanez, Toki, Greco..etc...The standard Japanese practice is the very top of the range models sometimes have a thin coat of nitro over the poly base coats. The rest of the production range, 90+ percent,... are finished in polyurethane. Some very top of the line guitars were all nitro,. but I never saw any.

    Boreas nailed the test so if the top layer melts and there is still finish...it's nitro over poly. If it all melts it's nitro only...and if it looks at you funny like "what the heck are you trying to do?"..it's 100% poly.
     
    Last edited: Sep 26, 2020
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  8. SC Relics Guitars

    SC Relics Guitars TDPRI Member

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    This is the 84 tokai after I finished clear coating it...

    9E6F9BAE-DCBE-46AA-8FF7-624EF6B26A62.jpeg

    Thick black urethane finish over a 1 piece alder body. There was definitely no nitro on it at all prior to stripping. Not to say they didn’t do it but I doubt tokai would have done anything other than polyurethane or polyester on these models. Needless to say it looked fab when it was all done.

    ACD4B6B6-29EF-44F2-8064-298DC0D07CB8.jpeg D8A4C3F7-0401-44A4-8AC0-DFF78243C5E0.jpeg

    As mentioned above, do an acetone test in an area that will be covered and see what happens.
     
  9. Boreas

    Boreas Tele-Afflicted Silver Supporter

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    Another point to keep in mind - hardness is not the same as toughness. In fact, they are often opposites. The harder something becomes, usually the more brittle it becomes, because it has no "give". A softer finish absorbs stress and may even leave a dimple, but won't fracture. So, poly is usually considered a tougher finish, nitro more brittle and less forgiving.
     
  10. Boreas

    Boreas Tele-Afflicted Silver Supporter

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    Nice finish!
     
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  11. Slippery Jack

    Slippery Jack Tele-Meister

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    Well, I tried the acetone test (I never knew that my wife had any), and to all of you doubters I say Ha! you were right, its poly. I still like it, though.
     
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  12. Slippery Jack

    Slippery Jack Tele-Meister

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    Anyway, back to the original point, I just touched up some finger nail dents in my new respray to fill them with paint. They would only have been noticed by me, but they irritated me. I'll leave them six weeks then sand and polish them out. I don't mind the usual dents and dings received in action, but these things borne out of stupidity straight after I'd done such a good job of the respray really needled me. I promise to be more careful in future.
     
  13. Freeman Keller

    Freeman Keller Friend of Leo's

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    For what it is worth, I usually can sand nitro a day after I shoot it while I'm building and leveling. However I wait 2 or 3 weeks after the last coat before I color sand and buff. It can't hurt and I've never had an issue waiting that long.
     
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  14. JuneauMike

    JuneauMike Poster Extraordinaire

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    Freeman, how would you polish a guitar body that's had several coats of nitro clear on it and shows only light orange peel, assuming you would be doing it by hand? Someone mentioned clay compounds, but I'm not familiar with that. I don't have a buffing wheel and am very reluctant to use power tools to polish it. But I also think wet sanding may not be in order in this particular case.

    final-top.jpg
     
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  15. Freeman Keller

    Freeman Keller Friend of Leo's

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    I don't know, I don't allow orange peel to get into my finishes. That really isn't facetious - if I had any orange peel in a color coat I would simply sand it out and apply a couple more. The last color coat should be perfectly smooth and level. If I got the orange peel in my clear coats I would simply sand out and apply a couple more coats. In each case I would figure out what was causing the orange peel and correct it (pressure, mixture setting, solvent base, yadda yadda).

    My final steps are always the same. I try to put down one last "flow" coat of clear diluted 1:1 which is applied fairly wet. With luck the surface is very smooth and pretty glossy. Depending just how good it is I start sanding at 800 or 1000, maybe even 1200 wet. Then 1500 and usually 2000. I buff with automotive "glaze" usually with medium and fine. I like Mequiers #2 and 3 but there are others, I don't want silicon or wax in anything I put on the guitar. I have a pedestal buffer but I usually just use a foam pad in a drill motor - you can get the pads at the auto parts store along with the glaze.

    People do buff completely by hand, I think you need to use a slightly more aggressive compound that I would use with a foam pad. The pad really isn't all that dangerous, the pedestal buffer can be.
     
  16. JuneauMike

    JuneauMike Poster Extraordinaire

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    Do you know what is taking place in the hardening process? Is the composition of the paint changing during that time, or is it just slowly gassing off?
     
  17. Freeman Keller

    Freeman Keller Friend of Leo's

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    My understanding is that nitro is strictly an evaporative finish, there is no reaction going on at all. The solvents continue to evaporate for a long time. Our friend Silverface will chime in and tell you that lacquer does not "cure", it "dries", which I believe is true.
     
  18. JuneauMike

    JuneauMike Poster Extraordinaire

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    Yep, I'm sure he will. And yes, it dries and does not cure. But apart from that, something is happening. The finish is not that hard an hour or so after its dried, but it seems to be harder weeks later. Professional finishers recommend waiting a long period of time before finish sanding or buffing. Makes one think that some sort of transformation is taking place.
     
    Last edited: Sep 29, 2020
  19. Boreas

    Boreas Tele-Afflicted Silver Supporter

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    Mental experiment: Take a small amount of lacquer and put it in a clear cup (smaller diameter the better) and mark the top surface level on the side. Watch it over a few weeks. The liquid solvent is what is gassing off. Liquid solvent takes up space. As the solvent leaves the cup, the level lowers and the nitro becomes more dense. The longer it sits, the denser it gets. The denser it gets, the "harder" it becomes. Eventually, when all of the solvent and volatiles are gone leaving just the solids that were in suspension, it actually gets brittle. But this takes decades, as any old Martin guitar will tell you. One way to think of nitro lacquer is think of glass. Glass is a liquid not a solid. Glass can settle over decades and can actually flow. That is why old windows look wavy. They weren't that way when new.

    Other coatings and paints just become one solid piece of plastic(?) after the volatiles are gone. I suppose that is what you would call cured.
     
    Last edited: Sep 29, 2020
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  20. JuneauMike

    JuneauMike Poster Extraordinaire

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    Thanks, I like that. I'd have to think that while those solvents are being displaced that the molecular structure of the paint is either changing or tightening, shifting or something.
     
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