Grading (salt)
Under grading refers to the increase in the (cooking) salt content in a brine in the salt works by natural evaporation by means of wind and sun . This saves heating energy when the brine is then boiled to produce salt.
In the saltworks of the 19th century, "degree" referred to the salt content of a brine, which could be determined with a special salt scale. “Grading” then meant increasing this salt content in the course of the manufacturing process.
history
The oldest known form of grading is box grading . It took place through evaporation of water as a result of the action of wind and sun, on the brine brought into large, wooden evaporation boxes. The clay and the poorly soluble constituents lime and gypsum settled on the bottom of the boxes and formed so-called grading stones . In order to keep the space required for grading within limits, the wooden boxes filled with stone over time could be increased. Even today you can see imprints of the wooden planks and beams of the graduation box on some of them.
In the 16th century, the first constructions of so-called leakworks appeared. They were small wooden boxes with tufts of straw inserted into them to increase the evaporation surface. When the weather was good, Lepperknechten doused them with brine.
In order to increase the effectiveness of the new system and to save space and personnel at the same time, walls made of straw were used at the beginning of the 17th century. The brine was then applied to the straw bundles from above with the help of pumping stations. The expectation placed in the new system was not fulfilled, as the brine ran off too quickly on the smooth stalks of the straw and too little water evaporated.
After attempts with birch twigs, which turned out to be less durable, the hard and durable blackthorn twigs were found to be the ideal solution to the problem at the end of the 17th century. As a result of the grading operation, the poorly soluble components of the brine are deposited on the black thorn and form gray to brown crusts, which over time grow together to form a closed stone, the thorn stone . The deposition process is intensified by the withdrawal of carbon dioxide from the sole, which takes place at the same time as evaporation. The color of the thorn stone is z. B. caused by traces of iron or manganese .
Effectiveness of graduation towers and subsequent use
High air temperatures and low relative humidity promote grading. Rain, fog and frost hindered the process. With an open construction, the wind can also hinder the effectiveness. With these boundary conditions, the operation of graduation towers is not possible in winter.
In many cases, only the graduation towers are left of the former, abandoned salt works. Today they sometimes still serve museum purposes or are used as open-air inhalers (see Halle (Saale) , Bad Orb ).
literature
- [6] , accessed on January 21, 2020
- Werner Schulze-Seeger, ORB, 1300 years of brine and salt , Orbensien-Verlag, 1994
- The salt boiler , Bad Orb, year 1, 2005
Individual evidence
- ↑ degree, m.. In: Jacob Grimm , Wilhelm Grimm (Hrsg.): German dictionary . tape 8 : Glibber – Gräzist - (IV, 1st section, part 5). S. Hirzel, Leipzig 1958, Sp. 1660 ( woerterbuchnetz.de ).
- ↑ Grading. In: Jacob Grimm , Wilhelm Grimm (Hrsg.): German dictionary . tape 8 : Glibber – Gräzist - (IV, 1st section, part 5). S. Hirzel, Leipzig 1958, Sp. 1687 ( woerterbuchnetz.de ).
- ↑ [1] , accessed on January 21, 2020
- ↑ [2] , accessed on January 21, 2020
- ↑ [3] , accessed on January 21, 2020
- ↑ [4] , accessed on January 21, 2020
- ↑ [5] accessed on January 25, 2020