The hard stone from Laoling or Gaoshan is simmered in rice fire to make the water in the stone evaporate, then it is dyed with black smoke oil while it is hot, and then the black is sucked into the cortex of the stone, polished and filled with Chushi. Experts call it "simmering black". However, Shijing is hot and stuffy, and there are often cracks. When scraping with a knife, the powder is still gray, and its black is only one or two centimeters from the cortex. Further down, it is still grayish white, while the real Chu stone is pink-green, even if it is scratched into a texture. Moreover, simmering black stone is light, and Chu stone is heavier than ordinary stone, so it is easy to argue. This kind of stew is very dark, and it is still everywhere. Another person who hangs Ken in pure black can also pretend to be Chu Shi. Black hanging Ken was originally black as faded paint, and its luster was better than simmering black, even better than ordinary coarse chushi. However, when it was scraped with a knife, the powder was gray, slightly deeper than simmering black, and it was light and easy to argue.