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Thread: stopping color change

  1. #1
    Join Date
    Nov 2006
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    Mountain Home, Arkansas
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    11,697

    stopping color change

    As we all know, many woods change color with time and exposure to light. Some beautiful colors are lost with woods like Osage Orange, mulberry, purple heart, etc.
    The culprit seems to be UV rays in light.
    I was recently told that the use of a (high quality) spar varnish as is used by boat builders will stop the color change.
    Locally, I found an off-brand of spar varnish for $15.00 a pint. I'm not inclined to experiment with such expensive stuff.
    Anyone here with boat building experience that has used spar varnish and can comment on this issue?

  2. #2
    Join Date
    Oct 2006
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    somewhere east of Queen Creek, AZ - South East of Phoenix
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    8,438
    don't know about spar arnish but I've been told that "Bull Frog" sunblock will work..
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  3. #3
    Join Date
    Jan 2007
    Posts
    810
    This not an answer, but a question that I've pondered for some time.

    One of my other hobbies is antique radios. I don't see any change in the colours of the wood used in these cabinets, whether made from solid wood or from veneer, even after 40, 50, 60 years.

    The difference that I can see is the method of staining. The traditional method of finishing radio cabinets was to seal with shellac, then spray with lacquer and to effect the colouration by using a wiping stain mixed with the lacquer.

    It seems that most woodworkers apply the stain directly to the wood and then apply whatever finish topcoat may be required.

    The question :: is there a chemical reaction between the wood and the stain that allows UV to work a change at a slow pace over the years, whereas the sealing effect of the shellac with a coloured topcoat prevents the change?

    just for thought ...

    cheers

  4. #4
    Join Date
    Dec 2006
    Posts
    535
    My sister the art conservator will tell you the only answer is a dark room filled with nitrogen.

    As far as I know, the trouble with UV absorbing compounds in spar varnish is that they eventually break down, with the varnish following shortly afterwards. I think they'll also settle out of the varnish, given enough time. I just used up the last jar I had of some spar, and there was a pinkish film on the bottom of the jar. I've no proof, but I'd bet that was the UV additive. I always have the paint store shake varnishes that have any kind of additive (like that minwax stuff with the pigment) and then let it set for a few days so the bubbles can dissipate. I always get a skeptical resistance from the clerk too, they always think I'm going right home to slap some varnish on something and warn me at tedious length about not shaking varnish.

    So anyway, I don't think there's any easy answer, sunlight just destroys stuff, whether its the wood or the finish. But if you don't mind refinishing every few years, the high quality spars might give you the best compromise.

    John

  5. #5
    Join Date
    Nov 2006
    Location
    Mountain Home, Arkansas
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    11,697
    John, thanks for that insight. What you say makes sense. I have been thinking about making a finish for penturners that is both durable and UV resistant. This would require buying the main ingredient in bulk and mixing with UV inhibitors then re-bottling for sale. But Ole Sol is, as you say, pretty persistent. I sure don't want to end up with 55 gallons of 'stuff' and a thousand small bottles I can't use. Or be out the money. Gotta go rethink this matter.

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