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And those paints that stay white in sunshine and yellow in the shade do so because of the catalysts in the paint that bleach the binder in sunlight. Sadly it's been so long since I did proper chemistry that I can't recall which catalysts do this. First formulated by ICI I think and used in Dulux paint.
For extreme environments there's a tendency to apply a two-pack urethane top coat varnish that screens UV from the layers below which stops colours from fading but may encourage white finishes to yellow.
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Precisely, it is never the pigment that fades, it's always the medium.
Stephen.
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On 15/06/13 13:02, snipped-for-privacy@btinternet.com wrote:

No. It isalways the pigment that *fades*, as the medium is transparent. You cant *fade* more than transparent, but you can *age* yellow.

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It also depends on the pigment as to whether it is permanent to light or not and AFAIK it is the carrier that yellows not the pigment.
Stephen.
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That is exactly what is happening.
Stephen.
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It's not the pigment which goes yellow, but the clear binder stops being clear and yellows. Doesn't need UV to do it either.
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Andrew Gabriel
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On 14/06/2013 21:56, Andrew Gabriel wrote:

Indeed. So, do we have any artists posting here who actually make their own oil paint. Let's get back to real D-I-Y!
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On 14/06/2013 21:56, Andrew Gabriel wrote:

Indeed. And some paint stays white where it has been hit by UV but yellows elsewhere.
Have to say, no problems whatsoever with yellowing of recent paint (last 2/3 years) - even where some has been touched up due to physical damage and so would highlight any changes. Mostly, but not exclusively Leyland/Johnstones. None of it true gloss.
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Paint it yellow.
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mark wrote:

+1. Then watch the yellow fade until it matches the white.
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Thanks for all of the advice. The wife is insisting that I use gloss again. I will not do this. I'll give it another coat of the water based stuff. Maybe I should have used two coats in the first place?

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