From Xinxiang Ceramic Mug Manufacturers,Four Methods of Ceramic Coffee Mugs Inspection:
"Look" is to have a close look at the inside and outside of the porcelain. To see whether the glaze of porcelain can be bright and smooth, with or without scratches, holes, black spots and bubbles; to see whether the shape can be regular and deformed; to see whether the picture has no defects; to see whether the bottom can be flat, it must be placed smoothly and without burrs.
"Listen" is to listen to the sound of tapping on porcelain mugs. If the voice is loud and pleasant, it is clarified that the ceramic tire is fine and compact, without cracks, and when fired at high temperature, the porcelain is complete. If the voice is hoarse, it can be judged that there are cracks in the ceramic body, or that the porcelain is incomplete. This kind of porcelain is liable to crack when it is changed by heat and cold.
"Contrast" is analogy. For matching porcelains, we should compare various accessories to see whether their appearance and picture decoration can harmonize and diverge. Especially complete sets of blue-and-white or blue-and-white compact porcelain, because the color of blue-and-white varies with the firing temperature, so they are blue-and-white porcelain with shade and depth. A set of several or even dozens of complete sets of cold porcelain, such as each blue-and-white color has obvious differences, this set of porcelain is greatly inferior.
"Test" means test cover, test fitting and experiment. Some chinaware has a lid, and some chinaware is composed of several components. When choosing chinaware, don't forget to cover the lid and assemble the components to see if it is suitable. In addition, some porcelain utensils have special functions, such as dripping Guanyin, which can drip water automatically; Kowloon Fair Cup, when the wine is filled to a certain position, will all leak light. So we need to experiment to see if its function is normal.
The content of lead and cadmium in glaze, underglaze and most part of glaze and white ceramics in ceramic cups is very low, but if the underglaze color ceramics use inferior pigments in the processing of ceramic flower paper, or use too much high amount of pigments containing lead and cadmium in the design of flower surface, or the temperature and ventilation conditions are not enough when baking, it is easy to cause the leaching of lead and cadmium to exceed the standard. Some white porcelain, mainly uncolored bone china, because of the use of lead-containing frit glaze, if the firing process is not strictly controlled according to the process conditions of bone china, lead dissolution is also very likely to exceed the standard.
Lead and cadmium in glazed and underglazed coloured ceramics are seldom or scarcely dissolved, so they can be purchased safely. If we pay attention to the quality control of various consumption links, the problem of excessive lead and cadmium can be controlled. From the past national surveillance and spot checks, not all products exceed the standard. The unqualified glaze decoration products mainly come from small enterprises of individual, private and family workshop type. The quality of products consumed and sold by large-scale consumer enterprises and regular dealers in big cities is comparable to that guaranteed.