What are the processes involved in making salt?

The islands in the East China Sea, since ancient times, the livelihood is limited, in addition to the sea, it is planting and salt tanning: those who planted rice paddies; salt tanning, salt fields; those who asked for the sea, the sea is also a vast acre of fields.

Salt field, we seaside people called "salt Tan", surrounded by the pond, the foundation with clay tamped, paved with glazed ceramic cylinder fragments, patted flat and solid, so it is also known as "cylinder valves Tan".

Cylinder valves Tan, with wooden or stone boards for the border, separated into a square grid, not only to prevent the brine overflow, but also as their own independent production units.

The usual water tanks used by the countryside, are some rough goods. Used to pave the salt field of the cylinder valve, is the second best of the waste products, the color is even more mottled. Therefore, the neat rows of salt fields, in the hot sun, looks particularly colorful. It's a pity that few people were willing to appreciate such a seaside flavor back then, they said, sun salt bitter death.

According to archaeologists, this "salt field sunning method" with the help of sunlight and wind power is a salt-making process that appeared very late. My hometown Yuhuan Island salt field prevalent, probably the Qing Dynasty Jiaqing, Daoguang years. Before that, the salt producers used the "frying method" to make salt, setting up a cauldron on a large stove, filling it with sea brine, and burning it to cook it. In those days, the salt people, called "Zaodu" or "Zaoding".

The governor of Yuhuan in the Qing Dynasty, Lu Yushu, had a poem entitled "Salt Pan", which reads: "Chessboard land is stained with salt and frost white, and the swan-face people steam the stove fire red. Ten miles square circle no other business, stall fire burning brine day rush." Salt pan, is the traditional salt-producing area of Yuhuan Island, three images appear in the poem, salt is very white, stove fire is very red, and the face of the person who cooks salt is very black.

To make clear the process and principles of salt tanning, I'm afraid I have to read three more years of chemistry books, for example, the outside of the salt field and ash tanning field, with gates to the sea water, the tanning field in the ash how to absorb seawater salts, and after several processes ultimately turned into salt brine.