Tuesday, July 26, 2016

What is it about dark gel coat?

Cleaner/wax application half done on the sheer stripe

What is it about dark gelcoat colors?  They seem to oxidize so much more quickly than the white.  Red is the worst, for some reason.  Dark blue is a close follower.

Could it be that their color absorbs infrared (heat) radiation more readily, making them hotter?  (Chemical reactions double in rate, roughly, for every 10° rise in temperature.)

Could it be that the white pigment (almost assuredly titanium dioxide) does a better job of protecting the interior resin from UV than the pigments used for the dark colors?

Or could it simply be that oxidation on white doesn't show because it is, well, white?  Actually, having rubbed out Eolian's entire hull several times during our ownership, I'd have to say that the oxidized layer on the white is definitely thinner than that on the green.

So I kind of think there is something special going on with the dark colors.  It is that way for automotive paint too...  the dark colors, and especially red, fail first.


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2 comments:

Unknown said...

Paint that accent band! I used one part marine epoxy paint on my bootstripes and it worked great, gloss is retained, and so easy. I rolled it on with a fine nap mini rolller and tipped it immediately with a wide chip brush.

Robert Salnick said...

Unknown -

How long has it been since you painted? Have you had to rub out the paint yet?

We have considered painting, but I am concerned about the longevity of the paint. The gelcoat has lasted 38 years, so far. And yes, it takes a little annual maintenance, but perhaps the important point is that it CAN be maintained. I fear that paint will not last anywhere near as long, and that it can only be rubbed out a couple of times before it wears thru and will have to be redone.

But perhaps I am wrong. What has been your experience?

bob

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