As early as 4000 years ago, our ancestors had made mirrors out of bronze. From Shang and Zhou Dynasties in the Bronze Age to Song, Yuan and Ming Dynasties, bronze mirrors were widely used as daily necessities. Among the ancient bronze mirrors in China, the bronze mirrors in the Warring States and Han and Tang Dynasties were the most exquisite. Some exquisite bronze mirrors have decorative and reflective white surfaces and have strong corrosion resistance. After thousands of years of abrasion, they still won't rust, and light can shine on people, leaving them unscathed. In the past, antique dealers called these bronze mirrors "Mercury Qin" and "Mercury Blue" mirrors. The rare phenomenon that the bronze mirror of "Mercury Qin" is white, bright and stainless has been discussed in China for nearly 400 years, and the research abroad has a history of half a century. Although people realize that the phenomenon of "mercury infiltration" may be obtained through some surface treatments, there are different opinions on its essence, formation reasons and manufacturing technology, and no one has ever copied it. Until 1986 and 10 in June, after more than two years' efforts, scientists in China finally unveiled the mystery of the Millennium rust-free bronze mirror of "Mercury Qin". Through the elemental analysis of the bronze mirror by researchers, it is clear that the mirror body of "Mercury Qin" is a ternary alloy of copper, tin and lead, and its composition is the same as that of ordinary bronze mirrors. The chemical composition of bronze mirror surface is different from that of mirror body. The mirror surface has a tin-rich layer, and the tin content is about 60%, which is 1 times higher than that of the mirror body. In addition to being rich in tin, the mirror surface also contains some metal elements higher than the mirror body or not. The tin-rich layer on the mirror is extremely thin, only a few tens to hundreds of millimeters. There is also a transparent tin oxide film on the tin-rich layer, and the corrosion resistance of the mirror is obviously greater than that of the mirror body. Through the test, the researchers finally understand the reason why the surface of the bronze mirror of "Mercury Qin" is always white and stainless. When making mirrors, ancient craftsmen used some surface treatment techniques to form a tin-rich layer on the surface. The polished mirror is white and slightly grayish yellow (the color of tin bronze changes from yellow to white with the increase of tin content), which shows that people are unscathed. The tin-rich layer is gradually oxidized in the air, and a dense microcrystalline transparent film with tin dioxide as the main component will be formed on the surface, which has excellent corrosion resistance. As long as this film is not destroyed, it can protect the metal inside the bronze mirror from corrosion and rust for thousands of years. What is the surface treatment technology of ancient bronze mirrors after the mystery of Millennium stainless of bronze mirrors was uncovered? It is still concerned by experts and scholars. According to the traces of polishing on the surface of the bronze mirror of the "Mercury Qin" in the Eastern Han Dynasty, Chinese researchers speculate that the ancient mirror-making technology may have adopted the "surface treatment of mirror grinding drugs". According to the statement that "mirror grinding medicine is also mercury and tin" in the book "Cold Mirror" and the clue that the mirror surface of "Mercury Qin" in the Eastern Han Dynasty contains other elements except tin, a white-gray mirror grinding medicine powder containing these elements was successfully prepared, and the mirror grinding medicine was rubbed with a felt ball, and the surface was as white as silver. After inspection, the surface morphology and state of the replica mirror are the same as those of the bronze mirror of the "Mercury Qin" in the Eastern Han Dynasty.