Blacklight test weirdness, guitars glow, that shouldn't

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by yelemusic, Dec 31, 2017.


Tags:
  1. yelemusic

    yelemusic Member

    Messages:
    8
    Joined:
    Mar 21, 2012
    Hi folks, this issue might have been discussed before, but I haven't been able to find a satisfactory answer.

    So here we go: I did said blacklight test on one of my old guitars, a 1975 Guild Starfire, which I expected to glow in the dark, and it did. No surprise here, since it's nitro lacquer.
    But I also tested a couple of other guitars in my possession, namely an Ibanez Artcore AFS95T, which I bought just a couple of years ago, and which should not be finished with nitro. Sure enough it did have this greenish glow. The headstock of the guitar is black, but under blacklight it glows green. It's harder to see on the body, because it's greenish under normal light anyway. But it glows!
    How's that possible? It's way to cheap a guitar to be finished with nitro.

    I then tested my old Takamine Hirade E90 classical guitar from 1984, which was a top of the line Takamine guitar back in the days, but still the finish shouldn't be nitro. It's way to durable and feels very much like poly or whatever modern finish they used back then.
    You guessed right, it also glows under blacklight. Some parts don't glow as much, like a bit that chipped and got fixed years ago, as well as other parts that you'd expect to have some wear. Nowhere though has the finish been worn to the wood (which a nitro finish on a well played guitar would have). So I highly doubt that it's a nitro finish.

    This got me thinking. They say, the blacklight makes nitro finish glow in the dark. What if blacklight makes other finishes glow too? It seems that this test is no reliable test whatsoever whether or not a guitar was finished with nitro. All it does, is expose repairs. But other finishes glow as well. Or do they?

    So did I get this wrong in the first place, and this test has never been a reliable way to identify nitro, or does this mean, that the guitars in question must have been finished with nitro, as unlikely as it might be?

    I'm really looking forward to your replies, as this got me well confused.

    And since it's December 31st, I wish all of you a happy new year 2018! :)

    Thanks!
     
  2. KGWagner

    KGWagner Member

    Messages:
    1,472
    Joined:
    Nov 28, 2009
    Location:
    Metro Detroit Area
    I doubt the test is worth much. Shine the black light on your teeth and see what happens. You'll be shocked to find that:

    A.) It appears your mouth has a lacquer finish
    B.) Your mouth is absolutely filthy
    C.) You're bad at brushing your teeth

    It's actually quite embarrassing. Which brings me to my point - there may be a lot of other things on the guitar surface that will glow that aren't finish. Tobacco, sweat, dust, oil, polish, who knows? Besides, why would lacquer glow and poly not?

    If you want to test for a lacquer finish, find a place that can't be seen and put a drop of acetone or fingernail polish remover on it. If it's lacquer, it'll dissolve. If it's poly, it'll just laugh at it.
     
    massacre and fretless like this.
  3. Guitarworks

    Guitarworks Member

    Messages:
    6,745
    Joined:
    Oct 8, 2007
    Location:
    Wisconsin
    To the best of my knowledge, the black light test in a dark room is used by collectors and dealers to verify if any part of a vintage or antique guitar, or the whole guitar itself has been re-finished, before they settle on a price. Supposedly, the more recent re-fin areas glow, while the original 50, 60, 70 year old nitro does not. So the idea is that if the guitar does not glow, it's legit and still has the original finish (I've never witnessed this in action and don't know how reliable it is). But if you're more interested in determining if a finish is nitro, then yeah, you'll have to use a solvent in an inconspicuous place to see if it reacts.
     
    massacre and bigtone23 like this.
  4. whoismarykelly

    whoismarykelly Oh look! This is a thing I can change! Supporting Member

    Messages:
    7,206
    Joined:
    Aug 30, 2006
    Location:
    Baltimore
    With a black light you're looking for inconsistencies rather than an overall glow. Places where a repair was oversprayed or glue lines where there shouldn't be glue lines. Stuff like that.
     
    Zeegler and massacre like this.
  5. yelemusic

    yelemusic Member

    Messages:
    8
    Joined:
    Mar 21, 2012
    Oh, so I see. The blacklight test does NOT say anything about whether or not it's nitro, it only helps to find inconsistencies in the finish.
    It's a fair point that all sorts of other materials will also glow. I didn't think of that, but it's of course something I should have been aware of. So it's not surprising that some of my cheaper guitars with poly finish would also glow in the dark.

    Thanks for our input, folks!

    :)
     
  6. whoismarykelly

    whoismarykelly Oh look! This is a thing I can change! Supporting Member

    Messages:
    7,206
    Joined:
    Aug 30, 2006
    Location:
    Baltimore
    You just have to know what you're looking for. Using a black light to test for finish is using the wrong tool for the job. There are other more conclusive ways to find out what is going on finish-wise. Black lights are fact-finding tools for making educated guesses about the history of an instrument. In most cases you're using one to find reasons not to buy an instrument or to gain leverage when settling on a price. And you're usually just confirming a suspicion. It's not going to be the first step in any inspection.
     
    massacre likes this.

Share This Page