Open-pan salt making

Open-pan salt making is a method of salt production wherein salt is extracted from the brine using vacuum pans. The brine is heated in a partial vacuum to lower the boiling point. In the past salt has been extracted by heating the brine in pans operating at normal atmospheric pressure, known as open pans.

Virtually all European domestic salt is obtained by solution mining of underground salt formations although some is still obtained by the solar evaporation of sea water.

Salt is made in two ways traditionally. Rock salt is mined from the ground. The other type known as white salt is made by the evaporation of brine. Brine is obtained in several ways. Wild brine streams, occurring from the natural solution of rock salt by ground water, can come to the surface as natural brine springs or can be pumped up to the surface at well, shafts or boreholes. Artificial brine is obtained through solution mining of rock salt with fresh water and is known as ‘controlled brine pumping’. A Bastard Brine used to be made by allowing fresh water to run through abandoned rock salt mines. A Salt-on-Salt process strengthens brine by dissolving rock salt, and/ or, crystal salt in weak brine or sea water prior to evaporation. Solar Evaporation uses the sun to strengthen and evaporate sea water trapped on the sea-shore to make sea salt crystals, or to strengthen and evaporate brine sourced from natural springs where it is made into white salt crystals.

This led to three types of salt production all of which used a variation of the open-pan salt method: Coastal salt production. The process involved solar evaporation of seawater, followed by artificial evaporation of salt using the open-pan technique in structures known as ‘salterns’.Inland salt production. The process used brine from natural brine streams flowing over buried salt deposits that was pumped up from the ground and evaporated using the open-pan technique.Salt Refining. This was a large-scale salt industry developed in coastal locations, based on a combination of inland salt mining and coastal salt production. Referred to as salt refining or salt-on-salt the process it combined weak brine from seawater with mined rock salt, and evaporated the brine into a white salt.

Open-pan salt production was confined to a few locations were geological conditions preserved layers of salt beneath the ground. Only four complexes of inland open-pan salt works now survive in the world: Lion Salt Works, Cheshire, United Kingdom; Royal Saltworks at Arc-et-Senans, Salins-les-Bains, France; Saline Luisenhall, Göttingen, Germany; and the Colorado Salt Works, USA.

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