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How to identify a nitro cellulose finish?

Discussion in 'Luthier's Corner' started by Jerry J, Apr 16, 2009.


  1. Jerry J

    Jerry J Supporting Member

    Mar 27, 2000
    P-town, OR
    I did a search and came with nothing.

    I recall reading that there is a way to identify nitro as opposed to poly but can't find it anywhere.
     
  2. Hi Jerry

    Nitro can be removed with lacquer thinner even after it's long dry, so you can see if it comes off with a cotton swab in an area normally under a pickguard, bridge, etc.

    Polyurethane finishes dry by oxidation/polymerization, so should not be removable with the same thinner, although they might soften a bit.

    This is not a sure fire way to tell if it's nitro though ...could be another type of lacquer. The only other way I know is to ignite a small flake of it. Nitro is chemically similar to smokeless gunpowder, and will burn furiously like a match head.

    Les
    L M Watts Technology
     
  3. odin70

    odin70

    Dec 26, 2007
    Nitro cracks after a while
     
  4. BillyRay

    BillyRay Supporting Member

    Jan 20, 2008
    Quebec
    If your bass resonates for day on end and the wood is breathing, you have a nitro finish. If not, you have poly and your bass probably sounds like a turd ;)

    Seriously, try the thinner trick under a pickguard or in the neck cavity. Poly also has a high gloss, thick, glass like feel that nitro can match, but it's usually less mirror like, especially on older finishes. Wear patterns around chips can also indicate wether it is poly or not. Poly finishes with chips will tend to look like scabs (small amount of bare wood surronded by thick paint all round). Nitro chips in a way that looks more even due to the thinner finish.
     
  5. 62bass

    62bass

    Apr 3, 2005
    Alcohol will soften nitro but not touch poly. Try a bit of methyl hydrate, available in paint stores and used as shellac thinner, on a hidden area. If it softens the finish it's not poly, or alkyd varnish or a host of other finishes.
     
  6. Jerry J

    Jerry J Supporting Member

    Mar 27, 2000
    P-town, OR
    Thank you so much for the responses. I just looked at a chip and it looks like a "scab".

    The bass in question is a mid '80's CIJ Jazz. The finish is very thin. For some reason I thought that the really early Japanese Fenders were painted with a nitro finish.

    BTW the bass actually does resonate for days.:) I got it on a trade.

    Thanks again for the help.
     

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