The main types of porcelain circulating in the market are ordinary daily use porcelain, bone ash porcelain, exquisite daily use porcelain, underglaze (medium) color daily use porcelain, daily fine ceramics, ordinary ceramics and fine ceramics cookware, etc. In addition to bone ash porcelain, other products are classified into superior products, first-class products and qualified products according to the number or range of appearance defects. According to the characteristics of flower surface, flower surface decoration can be divided into over glaze color, in glaze color, under glaze color, color glaze porcelain and some white porcelain without adding color. Glaze color ceramic is a kind of product which is made of glaze ceramic pigment and pasted on the glaze or painted on the product surface directly, and then baked at 700 ~ 850 ℃. Because the baking temperature does not reach the melting temperature of the glaze layer, so the flower surface can not sink into the glaze, only close to the surface of the glaze layer. If touch by hand, the surface of the product is concave and convex, and the height is uneven by naked eyes. The firing temperature of the color in glaze is higher than that of the color on glaze, reaching the melting temperature of the glaze. The ceramic pigment sinks into the glaze when the glaze melts, and is covered by the glaze after cooling. Touch the surface of the product by hand, it is smooth as glass, without obvious concave convex feeling. Underglaze color ceramics is a traditional decorative method in China. All the color decorations of the products are carried out on the ceramic body. After glaze application, the products are fired at a high temperature. Like the underglaze color, the flower surface is covered by the glaze layer, the surface is bright, flat, and there is no uneven feeling. The color glaze porcelain adds a kind of high temperature colorant to the glaze, which makes the glaze of the fired products present a certain color, such as yellow, blue, and bean green. White porcelain usually refers to ceramics without any color decoration, and the sales volume of this kind of products is generally small. The above different decoration methods, in addition to showing its artistic effect, mainly distinguish the content of heavy metal elements such as lead and cadmium. Among them, the lead and cadmium content of the glaze color, underglaze color and most of the color glaze porcelain and white porcelain are very low. If the inferior pigments are used in the processing of ceramic paper, or the amount of pigments with high lead and cadmium content is too large in the design of the flower surface, or the temperature and ventilation pieces are not enough when baking, because the frit glaze with lead content is used, the amount of lead and cadmium dissolved is a matter of human health Safety and health indicators. The less lead and cadmium in human blood, the better. If people eat the food with high content of lead and cadmium for a long time, it will cause the deposition of lead in the blood, and lead to the damage of brain central nerve, kidney and other organs. In particular, it will have a serious impact on the intellectual development of children.