There are two steps in the open molding process – gel coating and laminating.
During the laminating process, a reinforcing material (such as fiberglass, saturated
with catalyzed polyester resin) is applied to directly onto the cured gelcoat on
the mold, which forms a very structurally strong product. Gel coat alone does
not have the structural strength to be removed from the mold or to be used as
a final product.
There are two types of open mold laminating: hand lay-up & spray-up laminating.
Hand lay-up refers to the manual method of laying or applying the reinforcement
material into the mold. In the hand lay-up process, the reinforcing material
(usually fiberglass mat) is placed in the mold and then saturated with polyester
resin using a brush or a two-component spray system.
FoxValley Composites Inc. Hand Lay-up Fiberglass Process