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Old 06-12-2015, 01:00 PM
Admirals Club Admiral's Club Member
Join Date: May 2011
Location: South FL
Posts: 3,020

Originally Posted by Otseg View Post
Yes that is correct.

There are two classes of gel coat. Exterior and Interior.

The exterior is used in a mold first. It has what is called an air inhibited cure, Gelcoat iis 35-50% styrene, When the mold is coated, the styrene on the surface evaporates and is not available to link with the rest of the resin in the gel coat so the surface cure is inhibited.
Adding a laminating resin on top of the gel coat replaces the styrene and you get a chemical bond between laminating resin to gel coat.

Interior gelcoat has a wax additive which floats to the surface, prevents the evaporation, and allows the gelcoat to cure completely. This is the gel coat used as a coating, such as in the bilges.

Exterior gel coat can be used outside of a mold by mixing in a wax addative that comes to the surface and seals the gel coat from the air.

You don't want to get the two confused. :-)
Very interesting. Thanks
JoseG is offline