A graduation tower (also obsolete leakage works) is a system for salt production. It consists of a wooden frame that is filled with bundles of brushwood (mainly blackthorn). The verb gradieren means “to concentrate a material in one medium”. In the case of a graduation tower, the salt content in the water is increased by passing brine through the brushwood, which naturally evaporates the water. In addition, minerals associated with the brine, such as lime, gypsum and iron stone, are deposited on the thorns; this increases the quality of the salt produced.
Graduation tower in Bad Kösen
Many graduation towers are part of a salt works, which consists of a graduation tower and a saline. Graduation towers are often incorrectly referred to as "salt pans". Occasionally, rice installations in swimming pools are also referred to as graduation towers, which function like graduation towers, but are significantly smaller than comparable systems that are located in spa parks, for example.