The image of boys at play was associated with the happiness of having many sons, an ideal promoted by Confucian belief. Lacquer, a resin usually colored red with cinnabar, black with carbon, or, sometimes, brown, yellow, or green, was applied in thin layers on top of a wood, metal, or stiffened fabric core. The process of coating the sticky toxic lacquer with a brush, drying each layer, and re-coating to achieve a thickness suitable to carving was laborious, lengthy, and dangerous. Once dry, the surface was carved with a sharp, V-shaped tool.