hot/cold finish checking technique work for poly finishes?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by sleepykeith, Aug 8, 2006.


  1. sleepykeith

    sleepykeith Member

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    i've seen the results for nitro finishes, but wanted to know if they work for poly finishes as well.
    i know not everyone here is down with the idea of relic'ing guitars, but i've got an extra body that would be fun to experiment on.

    thanks!
     
  2. sleepykeith

    sleepykeith Member

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    was this a stupid question?
    i admit i know nothing about this stuff.
    any advice would be appreciated.
     
  3. n.j.

    n.j. Member

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    Not a stupid question. Personally, I have no idea. Try it and report back, I don't see how you could cause any harm if it doesn't work.
     
  4. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    Poly doesn't check like nitro does.
     
  5. Turbozag

    Turbozag Senior Member

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    actually it will check...

    I've heard stories and offer this only as FYI...

    Some have told me they freeze the bodies and then expose them to heat with a hair dryer etc to cause the rapid expansion/checking... I've never tried it and wouldn't on an expensive guitar.

    The pros mainly use an exacto knife to cut the lines by hand, then they use a heat gun (carefully!) to smooth the cut lines. Then some light sanding to finish smoothing the cut lines...

    They say it doesn't work on poly, but I've seen it done.
     
  6. chadbang

    chadbang Member

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    FYI

    I bought a can of Dust Off to try the freezing process on an MIM poly body. I went at it twice with no results. A couple days ago I was bored and REALLY laid on the freezing aerosol. I got two NASTY cracks. I'd read somewhere, too ,that poly doesnt get nice light "webbing" cracks aka "checking." But, rather, gets these deep cracks that go all the way through the thick poly finish. Correct! It was nightmare. I wound up having to try a superglue repair -- putting superglue into the thin cracks (thin but deep I should say) hoping it would seal up the fissure. Nope. Then I just had to sand down all the poly to get rid of the superglue "humps" What a bitch! After all that work, the cracks were still there, abeit smaller because I took the poly down so far. I finally just hit them with a black magic marker and I'm going to try and avoid thinking abou them.

    The ONLY good thing to come out of this relic knowledge-wise, was that I also tried using heat to "seal" up the crack. Also to no avail, but I did manage to put a series of Mini-warps into the paint (that bunching effect you see in old paint around the edges of things) in couple spots.I guess the heat warped the poly, giving it pseudo-realistic aged effect. But I think that's a very touch and go approach Luckily I was just using a strong hair drier, I hear with a real heat gun the paint might have just popped off completely!


    To make a long story short, avoid the "cold checking" technique on poly bodies - take my painfully learned less from one who tried and suffered.
     
  7. daddyo

    daddyo Guest

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    I've heard of 70s Fender poly finishes checking but I believe these were polyurethane finishes. Most poly guitars now including MIM Fenders use polyester finish which is essentially fiberglass resin. I guarantee that those finishes will never check. Split, yes, per Chadbang's unfortunate experience.
     
  8. Vhalia

    Vhalia Member

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    You can 'check' poly-sealed guitars, but it is time-consuming to get a realistic effect. I use a utility razor blade (just the blade) and with medium pressure, "draw" lines similar to what you see in tree bark. I work on small areas at a time, basically creating a "tree bark" design on the guitar. When I am finished, I use a scotch-brite pad or very fine sandpaper (1000 grit) and gently 'blend' all these cracks together by sanding away the high areas. Then I use a soft cloth, like an old T-shirt, and with my finger beneath it, tap it into Kiwi brown shoe polish and rub it into all of the cracks (checking) that I've created. The final step is to use a clean rag and run it all over. I've had excellent results using my method, and it works great as long as you have a lot of patience to do a good job.
     
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  9. TubeStack

    TubeStack Supporting Member

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    OP probably found his answer in the past 12 years.
     
  10. Killed_by_Death

    Killed_by_Death Member

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    It might be naturally roadword by now :p
     
  11. B. Howard

    B. Howard Silver Supporting Member

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    poly does not check like nitro..... no fine crazing. It just cracks and then the edges of the cracks will start to lift if the cause of the stress continues.
     

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