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 and 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.