Open-pan salt production was confined to a few locations where geological conditions preserved layers of salt beneath the ground. Only five 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; the Salinas da Fonte da Bica,
Rio Maior, Portugal; and the
Colorado Salt Works, USA. The two French saltworks at Salins-les-Bains and Arc-et-Senans became a
UNESCO World Heritage Site in 1982. The earliest examples of pans used in the solution mining of salt date back to ancient times when the pans were made of ceramics known as
briquetage and Cheshire VCP (Very Coarse Pottery), a coarse low-fired pottery. In Britain, these materials began to be identified from the early 1980s in the Marches (Herefordshire, Worcestershire, Shropshire and Wales) and later in Northern England. The Romans introduced small (3 ft square) pans made from
lead using wood as a fuel. In Britain they established towns for salt production at Droitwich in Worcestershire, and Nantwich,
Middlewich and Northwich in Cheshire. In the early Middle Ages these developed into the 'wich' towns of Cheshire. Small 'wich' houses containing several lead pans to evaporate the brine into salt, clustered around brine springs within each of the towns. The open-pan process continued largely unchanged throughout the medieval period. A 17th-century German wood-cut by Georgius Agricola shows the process in detail. Excavated evidence has uncovered wooden rakes to draw salt crystals to the side of the pan, and conical wicker baskets (barrows) in which the wet salt was drained and dried. By the 17th century, the pans started to be made from
iron, firstly in pans by . William Brownrigg writing in 1748, in his
Book of Common Salt, shows a wood-cut of one of these salt-making pans. The change to iron (from lead) coincided with a change from wood to coal for the purpose of heating the brine. Gradually, the pans increased in size. For example, Christoph Chrysel writing in 1773, in his
Remarkable and very useful Information about the present Salt Works and Salt pans in England, noted that salt pans were wide and long and deep. Brine would be pumped into the pans, and concentrated by the heat of the fire burning underneath. As crystals of salt formed these would be raked out and more brine added. By the 19th century, the open-pan salt process had reached its zenith in Britain. Two principal regions of production existed, Worcestershire and Cheshire. Brine shafts were sunk to the level of the brine stream that flowed over the natural rock salt or halite. Brine was pumped from the ground using wind and later, steam-driven beam engines, and redistributed to large iron pans. These fell into two categories: Smaller
fine pans were and about wide and about deep. They were housed in pan houses and had associated stove houses. The salt was evaporated in the pan at a high temperature of around . This produced higher quality grades of salt including 'Butter Salt', 'Dairy Salt', 'Calcutta Salt' and Lagos Salt'. After about six hours the salt would crystallise out of the brine solution and fall to the base of the pan. It was then the job of the
lumpman to rake-up the salt and skim it into wooden tubs to create lumps, hence the name. The lumps would then be sent to the stove house or 'hothouse' to dry. Here the lumps would be piled up and the recycled heat from the fires beneath the pans used to heat the room before exhausting through a chimney. The salt lumps would be 'lofted' or passed up to a warehouse above by a man called the
lofter. The lumps would be sold known as 'hand-it' lumps or processed in a crushing mill and then bagged. The second larger
common or
fishery pans were long x wide x deep and were built outside. The pans were usually heated by coal and were controlled by a
fireman. The larger pans would be heated at a much lower temperature between for several days or even weeks. This would produce a much denser crystal with a variety of sizes known as
common or
fishery salt. Common salt was used for a variety of reasons but included the chemical industry. Fishery salt was used in the packing and processing of fish. The salt would not be made into lumps but instead was skimmed and turned out onto the wooden platforms around the pans. It was then barrowed in large wooden store houses. ==Occupations in an open-pan salt works==