question: How is table salt produced and why was it so precious during the Roman times?
comment: There are two types of salt. Sea salt is produced by evaporating brine. Rock salt is extracted from salt mines. Despite the misconception, salt wasn't highly precious in Rome. Ostia's large salt marshes were readily exploited, and the Via Salaria was a very busy trade route because of it. Salt was more precious inland.
passages: Salt is extracted from underground beds either by mining or by solution mining using water to dissolve the salt. In solution mining the salt reaches the surface as brine, from which the water is evaporated leaving salt crystals.
  
  Section::::History.
  
  Section::::History.:Ancient world.
  
  Solnitsata, the earliest known town in Europe, was built around a salt production facility. Located in present-day Bulgaria, the town is thought by archaeologists to have accumulated wealth by supplying salt throughout the Balkans.
   In ancient Rome, salt on the table was a mark of a rich patron; those who sat nearer the host were "above the salt", and those less favored were "below the salt". The Roman historian Pliny the Elder stated as an aside in his Natural History's discussion of sea water, that "[I]n Rome ... the soldier's pay was originally salt and the word 'salary' derives from it ..."
   This process was made by running water through the region dirt, obtaining salt water; this water was boiled in pots to obtain salt after evaporating the water. It is confirmed that this city was a salt production center and that it provided up to 90% of the salt consumed in the valley between 600 and 700 AD. The salt was extracted from dirt in the southern part of the site.
   including a well and part of a preserved Roman road.
   Section::::Historical extracts concerning salt production in Middlewich.
  
  Section::::Historical extracts concerning salt production in Middlewich.:Camden's “Magna Brittania”, 1580.
   Major evidence of the fish salting and curing industry was uncovered during excavations in the 1970s and 1980s in the extensive Majuelo Botanical Gardens. These revealed the great extent of the rebuilding and modernising of the industry under Roman influence. A segment of the site has been carefully conserved, giving some idea of the size of the industry. This industry required not only large quantities of fish and sea salt, produced in many places along the coast, but also a constant supply of fresh running water.
   All through history, the availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC. Even the name Solnitsata means "salt works".
   In the early years of the Roman Republic, with the growth of the city of Rome, roads were built to make transportation of salt to the capital city easier. An example was the Via Salaria (originally a Sabine trail), leading from Rome to the Adriatic Sea. The Adriatic, having a higher salinity due to its shallow depth, had more productive solar ponds compared with those of the Tyrrhenian Sea, much closer to Rome. The word "salary" comes from the Latin word for salt. The reason for this is unknown; a persistent modern claim that the Roman Legions were sometimes paid in salt is baseless.
   BULLET::::- Flux: This ingredient was used to lower the melting point of the silica to form glass. Analysis of Roman glass has shown that soda (sodium carbonate) was used exclusively in glass production. During this period, the primary source of soda was natron, a naturally occurring salt found in dry lake beds. The main source of natron during the Roman period was Wadi El Natrun, Egypt, although there may have been a source in Italy.
   "From thence runneth Wever down by Nantwich, not far from Middlewich, and so to Northwich. These are very famous Salt-Witches, five or six miles distant, where brine or salt water is drawn out of pits, which they pour not upon wood while it burneth as the ancient Gauls and Germans were wont to do, but boil it over a fire to make salt thereof. Neither doubt I that these were known unto the Romans, and that from hence was usually paid the Custom of Salt, called Salarium.
   The dilute brine of the sea was largely evaporated by the sun. In Roman areas, this was done using ceramic containers known as briquetage. Workers scraped up the concentrated salt and mud slurry and washed it with clean sea water to settle impurities out of the now concentrated brine. They poured the brine into shallow pans (lightly baked from local marine clay) and set them on fist-sized clay pillars over a peat fire for final evaporation. Then they scraped out the dried salt and sold it. In rural areas of Sichuan, China, these traditional salt production methods lasted until industrialization in the 20th century.
   During the late Roman Empire and throughout the Middle Ages salt was a precious commodity carried along the salt roads into the heartland of the Germanic tribes. Caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt to inland markets in the Sahel, sometimes trading salt for slaves: Timbuktu was a huge salt and slave market.
  
  Salt in Chinese history was both a driver of technological development and a stable source of revenue for the imperial government.
  
  Section::::History.:Cities and wars.
   Salt may have been used for barter in connection with the obsidian trade in Anatolia in the Neolithic Era. Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, and salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salted fish and salt from North Africa throughout their Mediterranean trade empire. Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at Ostia to the capital.
   Lion Salt Works
  
  The Lion Salt Works is the last remaining open pan salt works in Marston, near Northwich, Cheshire, England. It closed as a work in 1986 and is now preserved as a museum.
  
  Section::::History.
  
  John Thompson Junior and his son Henry Ingram Thompson, a member of a family that had been making salt during the 19th century, started the Lion Salt Works when he built a salt pan in the coal yard of the Red Lion Hotel, Marston, in 1894.
  
  Section::::History.:Thompson family.
   Broken briquetage material is found at multiple sites from the later Bronze Age in Europe into the medieval period and archaeologists have been able to identify different forms and fabrics of the pottery, allowing trade networks to be identified. Saltworking sites contain large quantities of the orange/red material and in Essex the mounds of briquetage are known as Red Hills. A recent discovery at the Poiana Slatinei archaeological site next to a salt spring in Lunca, Neamt County, Romania, indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of Briquetage to extract the salt as far back as 6050 BC, making it perhaps the oldest saltworks in history.
   Salt was the fundamental seasoning: Pliny the Elder remarked that "Civilized life cannot proceed without salt: it is so necessary an ingredient that it has become a metaphor for intense mental pleasure." In Latin literature, salt "(sal)" was a synonym for "wit". It was an important item of trade, but pure salt was relatively expensive. The most common salty condiment was "garum," the fermented fish sauce that added the flavor dimension now called "umami". Major exporters of garum were located in the provinces of Spain.
   Salt was of high value to the Jews, Greeks, Tamils, Chinese, Hittites and other peoples of antiquity. Aside from being a contributing factor in the development of civilization, salt was also used in the military practice of salting the earth by various peoples, beginning with the Assyrians.
   Section::::Inland Open-Pan Salt Production.
  
  Open-pan salt production was confined to a few locations where 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.
   "For, there went a notable highway from Middlewich to Northwich, raised with gravel to such a height, that a man may easily acknowledge that it was the work of the Romans, seeing that all this country over, gravel is so scare: and from then at this day it is carried to private men’s uses. Mather Paris writeth that Henry III stopped up these salt-pits when in hostile manner he wasted this shire; because the Welshmen, so tumultuous in those days should not have any victuals or provisions from thence. But when the fair beams of peace began once more to shine out, they were opened again.
   At the cave, calcium nitrate, also called niter, is leached from dry soil. When Doctor Samuel Brown, a Transylvania University professor of anatomy, chemistry, and surgery, gave in Philadelphia, Pennsylvania in 1806 the first scientific description of Kentucky's saltpeter production, he drew mainly from the experiences of the Great Saltpetre Cave. As with most saltpeter caves, the land above the cave is a hardwood forest-covered plateau. Typically the saltpeter would be sent to Lexington, Kentucky to be made into gunpowder.
   The Vindolanda tablets are made from birch, alder and oak that grew locally, in contrast to stylus tablets, another type of writing tablet used in Roman Britain, which were imported and made from non-native wood. The tablets are 0.25–3 mm thick with a typical size being (the size of a modern postcard). They were scored down the middle and folded to form diptychs with ink writing on the inner faces, the ink being carbon, gum arabic and water. Nearly 500 tablets were excavated in the 1970s and 1980s.
   Section::::Longitudinal study of salt sites in Middlewich.:Wych House Lane Salt Works.
   Section::::Preservation.
   In ancient times salt was used as part of religious offerings in Egypt and even for preparation of the afterlife. Funeral offerings of salt were given to Egyptian tombs out of consideration for the deceased as well as food such as salted birds and fish to be eaten in the afterlife. Salt was used in combination with natron in the desiccation process. Salt was also used as a currency of trade between the Phoenicians and their surrounding empire of the Mediterranean. Researchers have suggested that even the Mayans salted their fish and meat to meet their dietary needs and to use it as a good which could be traded easily as it would be able to stored for longer times due to the preservative nature of salt. 
   Section::::Longitudinal study of salt sites in Middlewich.:British Salt.
  
  The only remaining salt works in Middlewich is the British Salt works at Cledford (SJ716644). This salt works obtains its brine from Warmingham nearby, rather than Middlewich. Salt from this works is sold by RHM under the Saxa brand.
  
  Section::::Regeneration.
  
raw_presuppositions: Salt was precious during the Roman times.
raw_corrections: Salt wasn't highly precious in Rome.