In fact, there is no problem with the normal use of bone china cups. The best answer is suspected of advertising, so I won’t talk about it. In-glaze and under-glaze colors are relatively single, because many pigments cannot be integrated into the glaze or covered by the glaze. The well-known underglaze colors belong to the "high-tech products" of the ceramic industry. However, the vast majority of people still pursue fine and beautiful patterns when buying dinnerware, and the overall style of the home is matched. Therefore, the simple colors of in-glaze and under-glaze colors are increasingly unable to meet the growing needs of customers. What to do if the in-glaze and under-glaze are to be sold, we can only try our best to advocate that the glaze is poisonous. Many foreign luxury ceramics are painted on glaze. The recent state banquet porcelains are also painted on glaze,and only on-glaze patterns can produce new patterns at a very low cost.
It is not ruled out that in the past, unscrupulous merchants used low-quality pigments and fired them at low temperatures, resulting in excessive lead and cadmium. But I am very sad to tell you that the market of ceramic pigments is now monopolized by foreign countries. The high-end pigments are made from Germany, while the low-end ones are made from Japan. Domestic pigments have always been based on empiricism, and the color of the pigments is unstable after firing, so they have basically been eliminated.
In addition, the process of overglaze color small film flower paper has been improving, not just the simple plastic film before, but also the kiln firing process, which is required by the national standard.
Since 2017, the country has vigorously controlled environmental protection. At present, the ceramic industry, and even the entire light industry, are facing the most severe winter. It is basically difficult to buy products with excessive lead and cadmium dissolution on the market.
Therefore, bone china manufacturers can conclude that there is no problem with overglaze coloring. If the temperature of baking and printing is normal during the production process (no low temperature baking), there will be no problems. The country pays more and more attention to environmental protection and sanitation. If there is a problem with the glaze color, it will not be available on the market, and it is impossible to use it for a state banquet.
In addition, seeing several other answers, there are actually many mistakes and omissions.
1. In fact, the underglaze color can also be applied to the clay tire, not completely hand-painted.
2. The plain body can be fired first, then glazed, and then fired twice. Now many bone china are fired in this way. The traditional method is to dry the clay body and then apply glaze, and fire it once, but the finished product rate of bone china will be lower when fired like this, and the drying process is not easy to control industrially.
3. Most of the in-glaze color is now the same process as the over-glaze color, that is, the formed white tire decal, the high-temperature firing melts the glaze, and the color blends into the glaze. This is a relatively new method of in-glaze production. In the traditional glaze, the upper and lower layers are covered with a layer of glaze.
4. All gold-edged dinnerware is glazed, because the heat-resistant temperature of the gold paste is less than 900 (the best gold paste is not good), and the firing temperature in the glaze is more than 1,000 degrees to melt the glaze.
5. Regarding the overglaze color, the general cost is higher than the underglaze and underglaze color. Carefully compare the prices of several types of products to know. The reason is also very simple because there are more colors, and the printing cost is high, and each additional color will be printed one more time. When firing, the underglaze color is formed again, and the cost is reduced a lot. The general cost of overglaze color is the highest. Therefore, it is nonsense to say that overglaze color is produced because of low cost. Note: The cost calculation here is based on similar products, excluding hand-painted products