Re: Whitening yellowed white guitar
I don't deal with guitar finishes a lot but I've worked in the industrial/residential paint market for about a decade now. I know guitar finishes are a bit different than what I deal with, but a lot of the newer finishes, like UV cured acrylic urethane, got it's technology from the industrial products I deal with every day. Both product lines have similar issues.
A few points:
1) UV cured urethane means that the product uses ultra violet rays to harden and cure. It doesn't not mean that the product protects anything from UV rays.
2) UV inhibitors protect colors from fading. They do not prevent yellowing.
3) Petroleum or plant oil based products (pretty much anything organic) will yellow over time.
4) Lack of UV will preserve color but accelerate yellowing. Yellowing is most noticeable on light colors.
5) An acrylic topcoat should not yellow. If it is clear though, the product beneath it can still yellow and show through the non-yellowing clear coat.
Any finish that is alkyd/oil based WILL yellow over time. It's simply the nature of the product. UV inhibitors will help keep color from fading. They will NOT prevent yellowing. LACK of UV will actually accelerate yellowing. We use to deal with this all the time with oil based paints. Paint the trim in a room with oil paint and watch the main room stay white for a long time with plenty of sun on it. Check the closet and see how yellowed the trim has gotten.
Waterborne finishes generally do not yellow. However, if the pigment or paint under an acrylic clear coat is an oil based product, it will still yellow, even if the clear on top of it does not.
Last edited by gideond; 07-23-2011 at 08:54 AM.