Date:         Thu, 13 Oct 1994 18:16:37 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         H Steven Dolan <dworkin@netcom.com>
Subject:      Re: Painting Pop Top



					H Steven Dolan
					dworkin@netcom.com

On Thu, 13 Oct 1994, Thom Fitzpatrick wrote:

> >As for gelcoating, I wonder how this differs from paint. Is it harder or less
> >resistant to fading or more waterproof or something. What is the deal with
> >gelcoat. Why don't we paint our cars with it if it is so good?
> 
> Gelcoat is a special coating put on the fiberglass that must be anaerobically
> cured.  It can then be painted like any other fiberglass part.  Most of
> the fiberglass parts you buy aftermarkety are gel coated.


Sorry to disagree, Thom, but Gelcoat is a two part pigmented epoxy resin
that is used as the exterior coat on fiberglass boats.  It is very hard,
and as a consequence, a bit brittle. Fiberglass is, however the same resin
bulked up and reinforced with glass fibers, so bonding between the two
resins is very good (which is why, other than a light sanding, no
undercoat {other than, perhaps, an unpigmented epoxy resin primer for
leveling effect} should be used) It is very waterproof when new, but over
time develops hairline cracks through which water can seep.  the lid will
remain quite as waterproof as ever, even yet, because it is the fiberglass
that keeps the water out, not the gelcoat.  The resistance to fading is a
function of the pigment and varies widely (you get what you pay for).  I
have seen new boats with bad fade and old boats with no fade.  I would
recommend a pastel as the brighter colors fade faster (but you were going
for white anyway, Martha?) As to why cars are not painted with this, most
2-part paints, if you read the label closely, are this same pigmented
epoxy resin.  Gelcoat is just the name I (a boater) use (probably
violating a trademark there, but who cares?).  I would hesitate to use
epoxy on broad expanses of metal because epoxy doesn't change dimension
with temperature and metal does.  I would worry about the bond popping
loose. 

Now that you have gotten to the bottom of this pedagogy, however, (he 
must be finishing, he used "however") I would defer to Derek, whose VW 
formula sounds an awful lot like a gelcoat analogue to me.

					H Steven Dolan
					dworkin@netcom.com