The grimace is not a walnut of literature and art, but actually a tree species. Ten years ago, there were not many seeds of this tree in the market, but now it is more common. There are different opinions about the origin of grimace. Some people say it's Indian, others say it's from the northeast of China.

In fact, the grimace of the domestic market is mostly produced in Guangdong, Guangxi, Yunnan, Hainan and other places in China, and also distributed in Southeast Asia. At present, there are large areas of artificial cultivation in all provinces of China.

In the process of playing, it needs to be cleaned frequently, otherwise it will also affect the coloring of walnuts. As we all know, after kneading walnuts for a period of time, there will be some mud hidden in the gaps in the gullies on the walnut skin, so cleaning is necessary.

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Back cover: seal the navel at the bottom with glue or candle oil to prevent the navel from leaking and promote the discoloration of walnuts.

Yellow skin: similar to negative skin, it is also a defect of skin color. Its characteristic is that some protrusions on the surface of walnut suddenly turn pale yellow with clear boundaries, and other skins turn red with kneading time, but the color of yellow skin remains unchanged, which is very unsightly.

Over-grinding: Some walnut dealers believe in the principle that "a standing walnut is a good walnut", and grind off the protrusions at the bottom of some walnuts so that walnuts can stand up.

Shrinking and smoking: It takes some time to dry new walnuts every year. Walnuts are harvested in September or even at the end of August in advance. Walnuts have a high moisture content and usually shrink by several millimeters within six months after being bought back.