Spraying materials after spraying equipment with a heat source, form injection, before reaching the by spraying the surface of the substrate, the flight time only a few thousand a fraction of a second or less. In such a short period of time, it is heating, melting or half melted, the small and dispersed droplet formation, ran to the substrate surface, be into flat folding shape small pieces, and the previously generated flat piece and is covered by the successor, quickly formed by many flat fold into the cover, is the spray coating. The higher heat humidity, drop impact velocity, the greater the formation of the coating is more dense. Coating performance is associated with many factors.