The general way of obtaining salt from the earth is by means of salt wells. These wells are drilled in the same way that wells are bored for oil and gas. A pipe about six inches in diameter is lowered to the surface of the salt rock and then an inside pipe is put down, water is forced down between the two pipes and the pressure exerted brings up the dissolved rock or salt brine through the inside pipe.
As the salt brine reaches the surface the salt is extracted from it in various ways. At present the crude open-pan system, where the brine was poured into open pans and fires were built below the pans, is almost obsolete. The most practical methods of refining salt today are known as the Grainer, Vacuum Pan and Alberger systems.
Bolters for Sifting Salt
The Grainer system is similar in its operation to the old open-pan system. The brine is run through long, shallow tanks and the heat is applied through steam pipes inside of the pan. The salt settles to the bottom of the pan and large rakes operated either by hand or machinery collect the salt.
In the Vacuum Pan process tiny cubes of salt are formed and settle to the bottom of the pan in which a vacuum has been created. The salt is then drained out and is ready for drying.
Variations of the two above processes make possible the production of certain grades of table salt. Oftentimes the brine is relieved of impurities through the action of certain chemicals. In some instances a chemical known as “barium chloride” is used, but the wisdom of this process has been much questioned, owing to the fact that barium chloride is a deadly poison.
