polyester is typically applied onto the waxed mold surface prior to spraying for cosmetic effect and for impact and corrosion resistance after the desired thickness is achieved the sprayed resin may be rolled against the mold to remove entrapped air and to insure uniformity typically the sprayed resin cures or becomes polymerized due to the action of a room temperature catalyst and a promoter it will be understood by those skilled in the art that mixtures exhibit low viscosities in order to be sprayed easily and evenly also entrapped air is easily removed during rolling of low viscosity mixtures and uniformity is accurately achieved when rolling such low viscosity mixtures thermosetting plastics such as unsaturated polyester resins are involved in a chemical reaction during processing which results in the extension and cross linking of the molecular chains to understand the curing mechanism of thermoset polyester it should be understood that the long chain linear unsaturated polyester as shown below reacts with a monomer such as styrene at the reactive double bonds to form a rigid infusible thermosetting material as shown below str1 for polyester spraying applications resin hydrate and fiberglass are typically used in the following concentrations ______________________________________material concentration______________________________________polyester resin 50 by weight of resin and hydrate including about 45 to 50 of a monomer such as styrene based on weight of the resinalumina trihydrate 50 by weight of resin and hydratefiberglass 10 20 by weight of resin hydrate.