THE GRADUATION WORKS OF 1638
In the year 1601, graduation works were introduced in Salina Sooden. Until this time, the brine with a salt content of approx. 4 % was boiled into salt - as was customary - in the boiling pans. The enormous quantities of wood, as the only fuel at that time, for over 80 boiling pans could no longer be provided. Therefore, the weakly saline brine had to be concentrated even before boiling.
Under the influence of sun and wind, water was absorbed from the brine trickling down from the large surface of blackthorn walls of the graduation works. The brine was concentrated by evaporation. In favourable weather, a brine concentrated to 25 % was derived. At the same time, a kind of filtration process took place, since the poorly soluble salts lime, gypsum and similar, which gave the table salt an unpleasant taste, were separated at the graduation works walls.
In the 18th. century, there were 14, sometimes even 22 graduation works. In the 19th century, there were only 7 remaining. The era of this kind of salt-making came to an end in 1906 - after nearly 2000 years. The loss of the salt works could be gradually made up by the thriving spa business from 1881 onwards.
The graduation works still in business today has a length of 140 m., is 12 m. high and exclusively serves the purpose of spa therapy. During graduation, individual salt particles (ions) are dispersed in the air so that this can directly enter the human body through the lungs. In the 334 m. deep shaft of the brine spring, a piston pump, which now hangs at approx. 50 m., sucks the 12 % content brine to the earth's surface.
The SALT MUSEUM opened in 1979 in SÖDER TOR provides comprehensive information on the local history of salt making from 58 AD.