At first, the materials for making colored glasses were obtained from the by-products produced in the bronze casting process, and were refined to make colored glasses. Glass has many colors, and the ancients also called it "five-color stone". By the Han Dynasty, the production level of coloured glaze was quite mature. However, the smelting technology is in the hands of the royal nobility and has been kept secret. Because it was difficult for people to get it, people at that time regarded stained glass as more precious than jade.
In ancient times, colored glaze, as a special material, belonged to the royal family, just like apricot yellow and dragon pattern. At the earliest, only the real royal family could use glazed products, and the manufacturing process of glazed products was also controlled by royal craftsmen.
Because of Fan Li, the discoverer of colored glaze, people think that colored glaze, like crystal, has the function of memory and inheritance. More importantly, colored glaze can bless the owner. "If you stay at home, you will become rich. If you live in an official position, you will become rich."
Around the Yuan Dynasty, with the appearance of man-made faults in the Han culture, many skills of the Han royal family were lost, and coloured glaze was among them. So in the Ming and Qing Dynasties, coloured glaze only appeared in myths and legends. You must have seen The Journey to the West. Friar Sand, who was the general of the shutter in the Heavenly Palace, was demoted because he accidentally broke a glass lamp. In Stephen Chow's words, breaking a glass will be demoted, and being a fairy is enough. But we can also see the preciousness of coloured glaze from here.
Before the Yuan Dynasty, China's glaze technology spread to the west, and westerners should have learned some fur, so this technology evolved into glass in the Venetian generation in the middle ages. Many western civilizations were handed down from China, but they did not retain the original technology. From glaze to glass, there are great differences in materials and technology, and more attention is paid to practicality and large-scale industrial production, but fundamentally, glass and glaze have already had essential differences, especially in culture.
Coloured glaze is known as the first of the five famous vessels in China (gold, silver, jade, colored glaze, ceramics and bronze) and one of the seven treasures of Buddhism. By the Ming dynasty, it was basically lost, only recorded in legends and novels of ghosts and gods. Friar Sand in The Journey to the West was expelled from heaven for breaking a glass lamp.
However, even in the Ming Dynasty, very incomplete craftsmanship was still protected by the hierarchy. At that time, the glass was very opaque, so it was called medicinal jade. "Ming system" contains: the accessories awarded by the emperor to the champion are medicinal jade, which can only be matched with more than four products.
The manufacturing process of ancient glass is quite complicated. It takes dozens of processes to take it out of the fire and put it into the water. The production of fine ancient glass is quite time-consuming, and some light production processes take ten or twenty days, and it is mainly made by hand. All the links are quite difficult to grasp, and the difficulty of grasping the temperature can be said to be half by skill and half by luck. Only one item is baked, and the yield is only 70%. More importantly, ancient glass is not as recyclable as gold and silver products. In other words, once there is a little problem, it will take more than ten days and dozens of processes, and many people's efforts will be in vain.