Hand lay-up is the simplest and oldest method of composite fabrication. It’s a low volume, labor intensive method used to manufacture boat parts, swimming pools, spas, automotive parts, among many others. Fiberglass mat and other reinforcing materials such as woven roving, knitted fiberglass, carbon, Kevlar, etc. is applied manually in the open mold. Resin is poured, brushed, or sprayed into the layers of reinforcement. Entrapped air is removed manually with squeegees or rollers to complete the laminated structure. Room temperature curing polyesters and epoxies resins are the most commonly used. Curing is initiated by adding catalyst to the resin system, which hardens with the above mentioned reinforcements, usually without external heat. For a high quality part surface, a pigmented gel coat is first applied to the mold surface.