Nitro over poly?

Discussion in 'Other T-Types and Partscasters' started by dcos, Jul 10, 2020.

  1. dcos

    dcos Tele-Meister

    Age:
    66
    Posts:
    127
    Joined:
    Jan 26, 2018
    Location:
    Sand Lake, Michigan
    So I'm refinishing the body on my kit built T style guitar with nitro. The neck is a Mighty Mite finished with poly. I'm bursting the body and would like to burst the neck where it meets the body. Do I have to worry about the two finishes reacting?
     
  2. schmee

    schmee Doctor of Teleocity Silver Supporter

    Posts:
    11,251
    Joined:
    Jun 2, 2003
    Location:
    northwest
    Usually the answer is no nitro over poly, but poly over nitro is ok. I have found however that "it depends". A thin coat of nitro can dry so fast it doesn't effect what's under it. Also, there are different poly's. Some are indestructable and some are just polyurethane.

    You could test in the neck pocket or wherever and see by brushing some nitro in there... then roll the dice.
     
    Fretting out likes this.
  3. jfgesquire

    jfgesquire Tele-Holic

    Age:
    53
    Posts:
    917
    Joined:
    May 23, 2018
    Location:
    Lake View
    I would think that was the opposite... that since nitro has to off gas you shouldn't put poly over it.

    Many Fender nitro finishes are just that.... Nitro over poly.... even 70s headstocks.

    Sent from my LG-H932 using Tapatalk
     
  4. Jim_in_PA

    Jim_in_PA Tele-Afflicted Silver Supporter

    Posts:
    1,557
    Joined:
    May 31, 2019
    Location:
    SE PA near New Hope PA
    "Poly" is not one specific product and the fact of the matter is that the solvents used with Nitrocellulose Lacquer can damage many other finishes including many containing polyurethane resins...but it depends on the specific products. Personally, I'd avoid applying nitro over "poly" and most other types of finishes. I actually do not even use nitro, preferring waterborne products for safety reasons.
     
  5. schmee

    schmee Doctor of Teleocity Silver Supporter

    Posts:
    11,251
    Joined:
    Jun 2, 2003
    Location:
    northwest
    Everything out gasses. But the problem is (I think!) is what the solvent does to the underlying finish. But I agree, a lot of it is technique and details. Maybe the Nitro lacquer solvent softens Poly if the Nitro is too thick.? Like I said, a thin coat dries very fast... often too fast to break down what's under it probably. Poly doesn't soften Nitro that I'm aware of. But some of all this seems a mystery in the real world for sure. I've used oil and water based stains under Nitro several times with no issues, although technically it's a no no.

    I think of it this way: If soak a rag heavily with Lacquer Thinner and lay it on a poly finish... it's gonna bubble up. If I have a little LT on a rag and wipe quickly, no problem. The real world part is : Duration, and Amount.
    I'm definitely no expert though.

    Due to the idiosyncrasies with Nitro I rarely use it at all anymore except on a vintage nitro guitar repair. Even Gibson has trouble getting it right sometimes at the factory...
     
  6. Telenator

    Telenator Doctor of Teleocity Vendor Member

    Posts:
    13,369
    Joined:
    Sep 19, 2005
    Location:
    Vermont
    ...........yeah but, that nitro with cancel out the tone stealing poly and make a dramatic improvement!
     
    schmee likes this.
  7. EsquireOK

    EsquireOK Friend of Leo's

    Posts:
    3,873
    Joined:
    Aug 30, 2011
    Location:
    U.S.A.
    Mechanical adhesion is really the issue. The solvents used for lacquer usually won’t dissolve a urethane finish. Test first, always, but the only polys I’d be worried about would be very old ones that are perhaps a bit degraded already.

    FWIW, the vast majority of Fender’s “lacquer” finishes since the ‘80s have been applied over urethane sealer.

    If you can scuff up the poly first, there’s no issue. I have painted lacquer over poly several times. It’s even better if you scuff up, and use dewaxed shellac as a transitional layer, and/or you can use a primer.

    The problem is with clear finishes. The scuffing that you do in order to help the lacquer “grab” the poly will likely be visible. So in that case, I’d use a finer scuffing product, like steel wool.

    All that being said, I don’t think it’s a good idea. I’ve seen burst necks, and they always look awful IMO. I would save the trouble, and keep the thing looking good, by not doing this.
     
    Biffasmum likes this.
  8. Jack Clayton

    Jack Clayton Tele-Meister

    Age:
    35
    Posts:
    489
    Joined:
    Oct 1, 2017
    Location:
    Phoenix, AZ
    This is a quote from the legendary Ron Kirn on putting nitro over poly. He said he his on another forum.

    "as far as applying it over the poly, the poly makes an excellent "primer".. simply "rough up" with something, around 240 grit, and squirt away....

    for those with their jaws still on the floor.... The "holy grail" of primer sealers used by Fender in the 60's, Fullerplast... and considered the definitive "correct" way to finish a vintage guitar IS POLY!!! Yo.... it's a catalytically cured coating...and every bit as difficult to remove as the most modern polys used today.... there's little difference chemically between that stuff and modern polyurethanes...

    Now, as far as No sonic advantage.. of course, every time ya do anything to a guitar it alters the "voice"... but a change is just a change...it can go either way...and considering that to make the change, you must completely disassemble the guitar, then redo it. including new strings, and whatever other "mods" ya planed to do while ya had it apart. How in heck are you gong to know what resulted in what change in sound? I'm still waiting for an answer for that one... been 'bout 15 years now...

    So anyway.. If you're gonna repaint it... leave the poly where it is... and you're half way "home".."
     
  9. musicalmartin

    musicalmartin Poster Extraordinaire

    Posts:
    6,518
    Joined:
    Aug 8, 2007
    Location:
    Norfolk UK
    I have sprayed red nitro over a Squier poly burst and it lasted years .I just roughed up the surface very slightly with some wet and dry .It doesnt attack the poly .Over time it reliced nicely but not quickly and nothing chipped off in huge chunks ,just the natural chips and dents like a guitar thats reasonably looked after gets so it all works .Poly,hardener and paint ,AKA urethene ,2K ,two pack ,etc is pretty bomb proof once cured and you can also spray it over nitro though the nitro will probably keep moving thus destroying your smooth finish as it wrinkles up the poly .
     
  10. 63telemaster

    63telemaster Tele-Meister

    Posts:
    336
    Joined:
    Jul 29, 2013
    Location:
    UK
    I bought a MIM tele a couple of years ago that had been refin'd black nitro over the original natural finish poly and it is wearing nicely. Presume the original finish was just knocked back enough to take the nitro. I gather the guy that did the refinish used to chip away the old poly finishes but no longer does this as it is too labour intensive/costly and that the original poly provides the perfect "primer" anyway.
     
  11. stratisfied

    stratisfied Tele-Meister

    Age:
    67
    Posts:
    206
    Joined:
    Dec 17, 2019
    Location:
    Midwest
    Home-applied polyurethane (varnish) will react to lacquer thinner. Maybe this is where your confusion lies.

    The catalyzed urethane and polyester finishes used by manufacturers and universally referred to as "poly" are not affected by lacquer top-coating. Fender has done this for years, top-coating their Fullerplast (polyester) sealer with lacquer on multiple models as others have mentioned.
     
  12. vhilts1

    vhilts1 Tele-Meister

    Posts:
    224
    Joined:
    Jul 7, 2010
    Location:
    PA
    why would you do nitro ....OVER....poly ?? that makes no sense....??.....if you want nitro sand the poly down then apply nitro....

    sound/tone/feel wise there is no discernible difference in a blind test tho.....

    looks wise nitro might win out in a retro contest however
     
    schmee likes this.
  13. ben smith

    ben smith Tele-Holic

    Posts:
    993
    Joined:
    Jan 16, 2019
    Location:
    london
    for me nitro over polly worked, it's the other way around that might not.
     
  14. Nick Fanis

    Nick Fanis Poster Extraordinaire Ad Free Member

    Posts:
    5,690
    Joined:
    Mar 3, 2003
    Location:
    Athens-GREECE
    All Fender vintage reissues ,apart from the pure vintage ones,are nitro over poly and they seem fine.
    All vintage Fenders (apart from the 50s ones) are also nitro over some kind of poly (Fullerplast &/or some poly based color) and they are still fine
     
  15. schmee

    schmee Doctor of Teleocity Silver Supporter

    Posts:
    11,251
    Joined:
    Jun 2, 2003
    Location:
    northwest
    Yeah, right on. No confusion, I said there are different "polys" in my first post.
     
  16. Jim_in_PA

    Jim_in_PA Tele-Afflicted Silver Supporter

    Posts:
    1,557
    Joined:
    May 31, 2019
    Location:
    SE PA near New Hope PA
    This is a VERY important point. The term "poly" is used very broadly sometimes for products that may be very different. Polyurethane and Polyester are components used to make finishes that vary in characteristics greatly.
     
  17. stratisfied

    stratisfied Tele-Meister

    Age:
    67
    Posts:
    206
    Joined:
    Dec 17, 2019
    Location:
    Midwest
    You take a MIM Polyester finished body and soak it in lacquer thinner all day and it won't soften the finish. This is why everyone who attempts to remove a factory "poly" finish resorts to heat guns and scrapers to remove the finish. In the end, they wish they had just painted over the existing finish.

    I once tried Aircraft stripper containing MEK (brain cell killer) on a factory applied Fender "Poly finish". It only dulled the paint and did not soften it sufficiently to remove it.
     
    jfgesquire likes this.
  18. jfgesquire

    jfgesquire Tele-Holic

    Age:
    53
    Posts:
    917
    Joined:
    May 23, 2018
    Location:
    Lake View
    The heat method actually works well. I was surprised how it's on top of the grain and came completely off. 20190713_195137.jpg

    Sent from my LG-H932 using Tapatalk
     
  19. ChubbyFingers

    ChubbyFingers Tele-Holic

    Posts:
    676
    Joined:
    May 28, 2020
    Location:
    Cypress TX
    Back to bare wood and start again IMHO.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.