Taking stock of the "wisdom of salt"! What methods did the ancients use to make salt?

Salt is an indispensable seasoning in human diet and is known as the "king of all flavors". Its importance is self-evident. Salt, in small seal script, is 鹽, which is a pictograph: "臣" represents ministers, "人" represents salt-making workers, "卤" represents brine for making salt, and "皿" represents the vessel for making salt. This character means that under the supervision of ministers, workers burn brine in vessels to make salt, which indicates that the salt-making process is a government act.

In ancient China, there were legends about "white deer drinking from springs" and "rams licking the soil". The ancients discovered the existence of salt by observing the behavior of animals. The history of salt production in my country can be traced back to the Shennong era (2370 BC - 2338 BC). Legend has it that a tribe called Susha under the Yellow Emperor invented the method of making salt by boiling seawater into brine and then making salt. Therefore, Susha was called the "Salt Saint". There is also an allusion "Susha Boiling the Sea" in the ancient primer "Thousand Character Classic".

Ancient salt-making diagram in "The Exploitation of the Works of Nature" Source: China Jiangsu Network

China has been planting grains since the Shennong era. Before that, the diet of ancient people was mainly based on animals and poultry, and the salt in animals was enough to supplement the human body's needs. However, after the main source of food became grains, salt intake was needed, and the method of salt production also came into being. From the perspective of salt production methods, salt can be divided into rock salt, well salt, sea salt, pond salt (lake salt), etc.

Sea salt is made by boiling sea water directly.

After the Tang and Song Dynasties, the production of sea salt gradually developed to the point where the beach was opened up, seawater was introduced and sprinkled, brine was obtained through sun drying, and then salt was boiled. This method was called brine boiling. During the Song and Yuan Dynasties, brine was poured and dried, that is, the concentrated brine was placed in a shallow pool and dried in the sun to crystallize into salt. During the Yongle period of the Ming Dynasty, my country began to build salt fields and directly dried seawater into salt.

Pond salt is the earliest natural salt discovered and used in China.

Pool salt is formed by evaporation and crystallization of brine in salt pools. It is produced in the northwest regions of Shanxi, Shaanxi, and Gansu. The most famous are Jiechi in Yuncheng, Shanxi, and Dingbian Salt Lake in Shaanxi. According to the "Historical Records", Huangdi fought against Yandi in Banquan and defeated Chiyou in Zhuolu. "The bloody battle between Yandi and Huangdi was actually caused by salt" to control salt, an important material. Later, the three emperors Yao, Shun, and Yu successively built cities in Pingyang (now Linfen, Shanxi), Puban (now Yongji, Shanxi), and Anyi (now north of Yuncheng, Shanxi), which indirectly confirmed this.

Aerial photo of Shanxi Yuncheng Salt Lake. Source: Visual China

Lake salt, also called pond salt.

There are two salt lakes in Qinghai Province, namely the Chaerhan Salt Lake and the Chaka Salt Lake, which are rich in lake salt. According to historical records, Chaka Salt Lake is one of the earliest salt lakes developed in China. As early as the Western Han Dynasty more than 2,000 years ago, the local salt had already enjoyed a high reputation in the northwest and central plains. The Chaerhan Salt Lake is the largest salt lake in China, containing enough salt deposits to feed the world's population for 1,000 years. Among more than 30 countries with lake salt resources, China ranks first, with reserves accounting for more than half of the world's total.

Chaka Salt Lake is known as the "Mirror of the Sky" Source: Visual China

Well salt is solid salt obtained by digging wells to extract underground brine and evaporate it.

Well salt appeared relatively late and the process was relatively complicated. As early as the end of the Warring States Period (255 BC-251 BC), Li Bing, a famous water conservancy engineering expert and the prefect of Qin Shu County, discovered brine during the construction of the Dujiangyan project and dug a 2-meter-wide and 15-meter-deep Guangdu Salt Well in Shuangliu, Sichuan. This was the first salt well in China.

Well salt production has been around in Sichuan since the Han Dynasty, and the Zigong salt industry developed during the reign of Emperor Zhang of the Eastern Han Dynasty.

During the Qingli period of the Northern Song Dynasty, Sichuan's salt industry made new technological progress, inventing the percussion drilling technology and drilling a new type of small-diameter salt well, the Zhuotong well. This salt well was the first in the world to use a drill bit, bamboo casing, and a brine pumping tube equipped with a one-way valve device.

During the Ming and Qing Dynasties, Sichuan's well salt production technology made rapid progress. In the 15th year of Daoguang's reign in the Qing Dynasty, the world's first 1001.42-meter deep well, the Shenhai Well, was dug. It has now been listed as a national cultural relic.

Shenhai Well Source: Sichuan Department of Culture and Tourism

Rock salt is salt deposited during the movement of the earth's crust.

It is usually formed after the lake or sea dries up, and is also called rock salt or mineral salt. Due to the different trace elements contained in different strata, different colors such as red, purple, blue, black, and white appear. Rock salt is directly mined from underground or on the ground using a technology similar to coal mining. "Records of the Grand Historian: Laws of the Western Regions" records that Gaochang (now Turpan) produced very delicious red salt and white salt, which is the earliest record of rock salt.

Image source: Visual China

The uses of salt are far more than just eating. It can also be used for sterilization, tooth protection, beauty, skin cleaning, decontamination, medical treatment, etc.

Potassium in brine is an important fertilizer raw material that can ensure the growth of food and crops; boron in brine is an important chemical raw material, which is indispensable for glass, instruments, etc.; magnesium in brine is an important raw material for aerospace and military industries.

There are also many trace elements in brine. For example, lithium batteries, the core components of new energy vehicles, part of their raw materials come from salt fields; the battery raw materials in mobile phones also come from the by-products of salt production.

Source: Popular Science Times

Author: Wang Heng, Researcher at China Science and Technology Museum