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If sunlight yellows the finish, why do covered areas yellow faster?

Discussion in 'Guitar Owners Clubs' started by MacFangus, Jul 8, 2020.

  1. MacFangus

    MacFangus TDPRI Member

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    Seems there's two camps... 1. Sunlight yellows the finish. 2. Sunlight bleaches the finish. One of my Gibson LP's has yellowed under the tailpiece, and under the pickguard. What's the deal?
     
  2. rangercaster

    rangercaster Poster Extraordinaire

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    Don't leave your guitar in the sun ...

    It makes them do strange, unexplainable things ...


    Jus' sayin' ...
     
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  3. archetype

    archetype Fiend of Leo's

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    First thing I'd suspect is that it's the original color under the tailpiece and guard and everything else that's exposed has bleached out a bit.
     
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  4. MacFangus

    MacFangus TDPRI Member

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    I don't see how it could be anything but. Others say exposure to sunlight... Mine are nitro finished. Maybe it's poly that yellows with sun exposure, reverse with nitro?
     
  5. archetype

    archetype Fiend of Leo's

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    It's mainly exposure to light, but sometimes other things. Lacquer and polyurethane both do it. Here's my '97 James Burton Standard poly finished neck. Spent most of its life in the case.

     
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  6. Dan_Pomykalski

    Dan_Pomykalski Tele-Meister

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    Not sure if you know already, but nitro has a yellow hue to it already, which is why Fender didn’t (doesn’t?) clear coat Olympic White instruments.
     
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  7. gobi_grey

    gobi_grey Tele-Afflicted

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    It is strange. My 2002 AVRI has no tan lines at all even though it's spent all of it's life out of the case and a lot of outdoor gigs in the sun.
     
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  8. EsquireBoy

    EsquireBoy Tele-Afflicted

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    I’ve always thought that sunlight was discoloring and fading the finish.
    To me the yellowing was coming from smoke, finger grease, etc.

    And indeed white can turn yellow when kept in the dark for a long time. It happened to me once with a nice wool sweater.
     
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  9. Dismalhead

    Dismalhead Poster Extraordinaire

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    I had a friend who built a guitar back in the '90s. Just tung oiled both the body and the neck. Stuck it in a closet in a case for 20 years and forgot about it. I asked him about it a couple of years ago and he pulled it out - the maple/tung oiled neck is now the most gorgeous deep amber you've ever seen. It sat in the dark.
     
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  10. EsquireOK

    EsquireOK Friend of Leo's

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    The sun does both. It yellows the binder (i.e. the hard finish itself), but it also bleaches the pigment (i.e. the color that is added to the binder). Usually these days, with “improved“ pigments, the yellowing is more rapid than the bleaching. But with enough sun, today’s pigments fade nonetheless. And there is variation from material to material. A highly UV resistant binder could very well show pigment fading before it shows yellowing.
     
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  11. johnny k

    johnny k Poster Extraordinaire

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    It would be interesting to see what happens to them in the full moon light.
    New finish ?
     
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  12. EsquireOK

    EsquireOK Friend of Leo's

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    This is false as can be.

    Nitrocellulose lacquer is crystal clear when fresh, unless it is tinted. And other than a very brief period early in the history of Oly White, it has been Fender’s standard practice to clear coat it.

    In the early days of Custom Colors being in the catalogs, Fender experimented with skipping clear on several colors. Oly White is the most famous, because it is the most obvious when the clear wasn’t used.

    It was formulated as a single stage acrylic lacquer, i.e. it wasn’t designed to be clear coated. So Fender took DuPont at their word and sprayed it that way at first.

    They soon discovered that the finish wasn’t as deep and brilliant, or as resilient, without clear, so they started clear coating it. If you’ve ever seen a late ‘50s to early ‘60s Cadillac with its original white paint, you’ve seen how poorly non-clear-coated early acrylics age. They don’t maintain their gloss very well, and they wear through more rapidly than clear coated paint.

    Clear was sometimes skipped later on, like in the case of a rush order. But other than early Oly White Fenders, it was always standard practice for the color to be clear coated. And when brand new, with clear coat, the original Oly White was actually a very slightly cool white, not warm in the slightest.
     
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  13. Dan_Pomykalski

    Dan_Pomykalski Tele-Meister

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    My sincerest apologies for unintentionally striking a nerve and offending you so deeply.

    I’m know I’ve read multiple times that Fender didn’t clear coat Olympic White because of nitrocellulose’s tendency to yellow. I may have been mistaken and remembered the author saying nitrocellulose has a yellow tint to it right away. I’ll try to find the source if I have the time...
     
  14. MacFangus

    MacFangus TDPRI Member

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    That's weird.
     
  15. MacFangus

    MacFangus TDPRI Member

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    My 2019 Gibson R7 came with an "aged Pelham Blue" finish, but it doesn't look all that aged to me. When I removed the tailpiece and pickguard, you could see a greenish hue; due to the yellowing against the blue, of course. Why would the finish yellow underneath the TP and PG only?
     
  16. Irondog

    Irondog Tele-Meister

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    apparent colors of paints Woods and lacquers are complicated.
    I am a chemist.

    So yellowing is the easiest oxidation to observe especially on lacquers.
    The true phenomenon is simply called "oxidation"
    almost every finished surface on earth oxidizes. Certain metal alloys are designed not to oxidize in our lifetime.
    the awesome thing about oxidation is it almost always changes the chemical compounds color.

    It is the ultraviolet spectrum portion of the sunlight that accelerates oxidation processes. ultraviolet light accelerates oxidation. As well as other chemical reactions. tars and nicotine's from cigarette smoke can help in 2 ways... tar is a stain it can add color it can also speed up oxidation.

    the color of a guitar changes in multiple ways. you typically have 3 components oxidizing at different rates.
    1. The wood oxidizes and changes color as the bottom layer.
    2. The stain and sealer oxidize and change color.
    3. The lacquer or final coat. Especially tung oil and linseed oil continue to oxidize all by themselves with no help from the sunlight.

    so a layer of light blue maple, then colored or overlaid by a red dye with an additional layer of yellow lacquer. You can get some weird colors/tan lines. 3 transparent colors blended together

    I used to work building houses there are multiple studies showing how different woods oxidize and change color in much different ways depending on the type of wood. This was specifically to help you choose what color to stain your decks or siding of your house. How it would oxidize in 5 years.
    Pine can turn slightly yellow Oaks can turn grey, Maple turns light gray. redwood turns black.. so on and so forth each wood oxidize in different colors.

    good times at the okay corral.
     
  17. Dacious

    Dacious Poster Extraordinaire

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    jagw65cp.jpg

    Here's an Olympic White Jag with pickguard off that was clearcoated. Matching headstock. You can see where the pickguard s gone the nitro is still clear.

    Here's my 78 with polyester finish - I suspect they sealed the timber with Fullerplast or similar then shot a single coat of this stuff. It's (501) Blond.
    78_tele_fade.jpg

    Here's my 69 RI built '96 - spent most of its time in the case. The neck on this guitar was almost white when new. Poly paint, maybe not gone as dark as nitro might.
    IMG_20180808_115649.jpg

    If paint's gone dark when covered, it's reacted in some way, or not outgassed properly. Possibly topcoat affected by something underneath.
     
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  18. Dacious

    Dacious Poster Extraordinaire

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    And here's the Thinline today. When new, the body was a light tan. The neck was very pale. Just a hint darker than a new US Standard satin finish. It's now a rusty-russet colour, with a yellow brown to the neck. Not a few people have asked if it's a 'real' one.

    IMG_20200711_181049.jpg
     
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  19. MacFangus

    MacFangus TDPRI Member

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    If it's sunlight that causes oxidation, why has the nitro underneath my R7 tailpiece and pickguard yellowed? Since those areas are more or less blocked from sunlight, one would expect the opposite.
     
  20. EsquireOK

    EsquireOK Friend of Leo's

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    This was explained above. That just means that your pigment is fading faster than your binder is yellowing. It means the guitar was painted with a highly UV resistant lacquer.
     
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