In order to improve and beautify the surface state of FRP products and improve the value of the products, and ensure that the inner glass steel is not eroded to prolong the service life of the products, we usually make the work surface of the product into a layer of resin with a high content of resin with pigment paste (color paste). It can be pure resin or be reinforced with surface felt. The adhesive layer is called gel coat (also known as the surface layer or decorative layer). Production quality of gel coat will directly affect the product quality and the external resistance, water resistance and chemical resistance of erosion etc. Therefore, the following points should be paid attention to when spraying or painting the coating.