? Well salt well fire boiled salt.
? Stir-fried salt in seawater
Salt is a necessity to maintain human survival. The history of salt production in China can be traced back at least 5,000 years ago, which is almost synchronous with the history of Chinese civilization in the history books. According to the source of salt, ancient salt in China can be divided into sea salt, lake salt, well salt, rock salt, etc. The production process of each salt is different.
China has a long coastline, and people began to produce sea salt very early. Before the Tang and Song Dynasties, sea salt production was relatively primitive. In the early stage, the salty soil on the seashore was scraped directly, and then the seawater absorbed by plant ash was used as the raw material for salt production. When making salt, the above raw materials are washed with water to dissolve the salt and form brine. Then the brine is put into an open container, and the water is evaporated by heating to obtain salt particles. This method is called pickling. It is worth mentioning that before frying salt, it is necessary to dry the brine to increase the concentration of salt. People usually put lotus seeds into salt water, and determine the concentration of salt water according to the shape and fluctuation of lotus seeds. The principle is exactly the same as that of the current densimeter. After the Song and Yuan Dynasties, many coastal areas gradually used sun-dried salt instead of fried salt, saving a lot of fuel costs. In some places, sea water was introduced by topography, and a series of salt ponds were built at the seaside, which saved the salting process.
Most of the lake salt comes from the salt lake area. Besides the Qinghai-Tibet Plateau, the most famous salt lake in ancient China is Yanchi in Yuncheng, Shanxi. The production technology of lake salt is basically the same as that of sea salt, and most of them are sun-baked.
Rock salt, also known as salt mine, is actually a solid salt-bearing rock stratum deep underground. There are two main ways to mine ancient rock salt. The first is to dig tunnels and extract salty rocks. Then the rock is crushed and dissolved to extract salt. The second is to dig a deep well to the salt-bearing rock, inject water to dissolve the salt to form brine, and then extract the brine. This method is the same as the production process of well salt.
Among the ancient salt-making processes, the production process of well salt is the most complicated, which can best reflect the wisdom of ancient Chinese people. The production technology of well salt has experienced a continuous development process. As early as the end of the Warring States period, Li Bing, the prefect of Shuqin County (the date of birth and death is unknown), had dug a salt well in Chengdu Plain to collect brine and stir-fry salt. At that time, the diameter of salt well was large, and the shaft wall was easy to collapse without any protective measures. In addition, the water depth is shallow and only shallow brine can be extracted. After the mid-Northern Song Dynasty, Zhuo Tong Jing appeared in southern Sichuan. Zhuotong well is a small deep well. When sinking a well, use a straight drill to impact and break the rock, inject water or use groundwater, and suck out the cuttings and water with a bamboo tube. The borehole diameter of Zhuotong well is only the size of a bowl, and the borehole wall is not easy to collapse. The ancients also removed the knots of bamboo, sleeved them end to end, wrapped them with hemp rope, coated them with putty, and lowered them into the well as casings to prevent the shaft wall from collapsing and soaking them in fresh water. When taking brine, thin bamboo is used as a brine absorption tube, which is inserted into the casing, and the bottom of the tube is used as an on-off valve. A cylinder can pump several barrels of brine, and a large wooden frame is put on the well to pump brine with pulleys and carts.
The emergence of Zhuo-barrel well marks the maturity of deep well drilling technology in ancient China. Since then, the depth of the salt well has been increasing. In the 15th year of Daoguang reign (1835), the world's first deep well shēn was drilled in Zigong Salt Area, Sichuan.