Common
[NaCl] - SALT.. made the world go round.
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Continuous and reliable supplies of Salt, were a matter of such importance that the establishment of early settlements, the rise and decay of civilisations, demographic shifts of populations and the development of agriculture, were intimately related to the immediate availability of salt. The power to control a population's salt supply, was power over life and death. Erratic sea level changes, particularly in the Mediterranean prevented some of these civilisations from obtaining consistent salt supplies, causing them to migrate or decay, conquor or succumb to others.
PRODUCTION OF SALT
- Boiling - Solar pan evaporation - Rock mining - Saltpeter - Tinder - Gunpowder - The East India Company -Glass - Leather - table salt -
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Salt is physiologically absolutely necessary for human life, but in the past the known mineral sources were limited, so much so, that it was a critical demographic power factor for most communities, until industrial means of extraction from brines were devised. It was only available as visible and exposed rock outcrops, in arid regions, and as dried out salt cake on the shores of seas and salt lakes. In areas with wet climates, the protruding salt dissolved making it almost impossible to discover. It is probably this, more than for any other reason, that some of the great civilisations first developed near deserts and desert climates, for example the Mediterranean region, at the edges of the "arid" zones.
Solar evaporation on coasts was considerably easier, than manually quarrying and hacking at rock salt. A large share of the world's consumption of salt - is still made by the ancient methods of trapping seawater or salt spring brines, and evaporating the brine and concentrating the salt, either artificially, or under the sun's heat.
World salt production totalled 190 million tonnes in 1994 see Salt Institute statistics
Table Historic Salt production per man employed [known figures]
Period Locality Quantity/year (tons) Men employed Method ofProduction One man makes
per year (tons)
1900 Taodeni(Sahara) 4000 250 primitive mining 16
1900 Coserra(Italy) 6000 250 primitive mining 24
1890 Sicily 17,000 400 primitive mining 43
1660 Tirol(Austria) 12,000 250 (+300 for
gathering wood) brining 48 (22)
1700 Rhe’(France) 4000 250 solar 16
1960 Reichenhall(Germany) 100,000 400 brining 250
BRINE PRODUCTION
Ancient coastal salt manufacture depended on the availability of wide flat coastal areas and in making clever use of natural, shallow deprssions, lagoons or manmade salterns about 15-20 cms deep. These had to be positioned at mid-tide level to facilitate filling [without industrial pumps], the evaporation pans in order to concentrate the brine, and later for harvesting and drying the precipitated crystallised salt.
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 China
- Drilling for salt circa 400 AD - to depths of 3000 feet" |
Chinese technology included drilling into a salt deposit,
at least two holes:
one hole to feed and flood fresh water from a nearby source into the salt
diaper, and the second hole to allow the water to 'well' up after dissolving
the salt, into evaporation pans, where it could be again concentrated by
evaporation.
It takes approximately, 50000 cubic/m of sea water spread over 100000 sq/m, of flat evaporation area, to produce 1000 tons of salt a year. There are two other important conditions:
- # an equable climate with a warm breeze and a hot sun
- # a reasonably steady sealevel. [The Mediterranean tide fluctuates only a few centimetres, whereas the oceans may have tides of more than than some metres]
Such areas were abundant when the sea was one or two metres below its present level; they became comparatively rare with a sea level of one or two metres higher, Even in Delta areas of the some rivers, like the Nile, Rhone, and the Euphrates, the establishment of new pond levels was very difficult.
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Table |
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Tons of fuel |
Fuel | Source of fueland salt | Method used | Location | Year |
| 4 | wood | brining and wood gathering on 100,000 sq/m woodland per year | 'camp' fire | Tyrol | 1600 |
| 14 | peat | Ocean water | Ash extraction | Jutland | 1650 |
| 6 | coal | Ocean water | Open pan | England East coast | 1700 |
| 1 | coal | Brining | Open pan | Cheshire | 1700 |
| 0.2 | coal | 20 kw/hr | Vacuum pan | Germany | 1950 |
| 0.02 | coal | 200 kw/hr | Vacuum pan - compression still | Switzerland | 1950 |
| 0 | solar energy | 100 sq/km of flat impermiable pan area at ocean tide level | Solar pan | Mediterranean |
1950 |
.A change of climate conditions, or a minor ocean fluctuation could have had a serious effect for ancient coastal saltmaking. Manual rock mining or inland salt springs or lakes like the Dead Sea suddenly became the only alternative.
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Techniques
Among other important concepts to move the huge quantities of brine, and technical innovations developed in producing salt, were the measurement of density and pumping by screw, both ascribed to Archimedes. The first use of impellars and sail type windmills was to operate an Archimedian screw and chain pumps for controlling water and brine flows.
Boiling
In regions where solar energy could not be used the saltmaker was forced to use solid fuel to 'boil' brines. In northern Europe, [PEAT PRODUCTION OF SALT] - it was primarily peat, and also wood. Whole forests were devoured leaving only the stumps.
In Japan it was seaweed.
Luneburg Salt well before 1500 - In 1569 the well was converted to a pumping system Up to the year 1569 the brine was won out of the "Sod" (well pit) with a barrel-like jar called "Öseammer". The workers of the salt works called "Sodeskumpane" had to lift up the jars with their own muscle power. A kind of seesaw called "Sodrute" served as a lever. When visitors come upstairs from the basement they stand in front of a faithful copy of such a "Sodrute" with a "Öseammer" hanging from it.
Solar pan Evaporation
Crystallisation of salt in solar pans in hot climates, occured naturally.
The crystals first form on the surface of the brine, until they become
soaked - since the surface brine reaches saturation point before the cooler
lower layers. Additional crystals grow beside these crystals which become
partially submerged, rather than below them, or above them, and a typical
"funnel" or 
Salt mushrooms growing
in the Dead Sea
wedge shaped form of crystals takes shape. The familiar salt "mushrooms"
can be seen growing in salt lagoons and pans.
The specific gravity of a Sodium Chloride crystal is 2.16. and the
saturated brine at 25 C contains 26.7% salt. and has a specific gravity
of 1.2004. At 15 C a saturated solution contains 26.5% salt, and has a
specific gravity 1.203. Hence a solution saturated at a higher temperature
is specifically lighter, even though it contains a greater quantity of
salt. It is this explanation that allowed salt makers to crystallise
"blocks" or briquettes of salt on the surfaces of ponds, using
floating elements such as sticks and straws to form the crusts of salt.
. It should be noted that with most other substances, crystallisation
can not occur at the the solution surface because their solubility increases
more rapidly than their specific gravity decreases. [see
Jewish Salt Technology - Religion]
Dikes enclosing solar evaporation ponds and pyramids of raked-up salt
At the end of the last Ice Age, around 17-15000 BC, the ice sheets covering the earth's surface began to retreat, flooding the continental shelf where many early populations seem to have lived. The average mean sea level rise was about 1 metre a century, the most rapid period being betwen 8,000 and 5,000 BC By about 2000 BC the oceans had recovered from the Ice Age lowlevel, risen again and had probably reached a metre or so above today's level.
Sea level variations, either seasonal, short lived or long term may have been caused by different events or a combination of them. Among the most obvious, may have been changes in atmospheric pressure, changes in ocean currents, wind driven waves, storm surges, heavy rainfall increasing the run-off from rivers.
However, as the last ice age has demonstrated, [and of present concern regarding global warming,] the colouring of Antarctica with Volcanic ash, or other pollutants and the subsequent warming and melting, of the polar ice sheets and glaciers was, and is, of catastrophic proportion in comparison Control of the colour of the Antarctic ice cap may be our immediate concern in the near future.
ROCK MINING and PRIMITIVE SOURCES
Many regions of the Earth, for instance equatorial Africa, consist of igneous rock where rain and ocean spray dust are the only sources of salt .Plants exist which are capable of concentrating such dilute solutions by evapotranspiration, and there are insects which can collect salt from water containing less than 0.006% of chlorides and concentrate them in their bodies to about 0.3% . Until recently some humans survived solely by drinking the blood and urine of herded and wild animals. Roaming over wide areas these animals collected and concentrated the salt in their blood by feeding on large quantities of plants . (Man tribes like the Masai kept their animals alive for systematic bleeding.) Springer's map of precolonial Africa shows immense areas where this happened and the low population density of the African hinterland can be ascribed to this diet of near salt-starvation . Furthermore, there is no doubt that early settlements grew up around salty springs which hunting tribes had discovered by following animals to their salt licks.
Another remarkable source of salt is registered in Springer's map, namely where people burned plants to use the resulting ash as a supply of very poor grade salt; in effect they replaced the stomach of the ruminant animal by combustion. One might almost call it the first primitive agriculture. Shcultz a describes how "... in the Brazilian rain forest, deep in the Amazon river watershed, live the Suya people. Their women collect water hyacinth, dry them and burn their leaves. The ash is then passed through a kind of grass filter after it has been dispersed in hot water. The filtrate is evaporated in an earthenware pot over a wood fire until it becomes a thick brown sauce which jellies to a dirty coloured mass when cooled down . This, divided into minute portions, serves as spice..."
Although this ash is too rich in potassium carbonate to serve as a good source of salt, it is almost the only way to avoid salt starvation. The other alternative is cannibalism19b. As Springer points out, "It is known that salt-starved animals eat part of their litter in order to stay alive, and consequently several authors have ventured the opinion that extreme salt hunger is one of the causes of cannibalism. This seems to have become habitual in parts of Africa and New Guinea where people have been subject to serious salt deficiency for a long time..." Primitive man living in rain forests far from the sea suffer the same deprivation , as generally it is not practicable to transport ocean water, with its 97% water-content, deep inland. The aborigines in New Guinea, however "... make secret expeditions to the sea coast.... to put seawater into hollow bamboos which are carried back to their tribe.. ,
There were many early attempts to quarry and mine salt. Salt tunnels containing stone hammers and axes have been found at sites in Asia Minor, Armenia, South America and near the salt river civilization in Arizona. The Hallstadt salt mines in the Austrian Alps and the Italian mines in Lungro, Cosenza and Etruscan Volterra supported prehistoric communities forming important centers of inland civilization. , Surprisingly, very similar specialized tools were used in all four continents. , , The production of salt from concentrated brine is much easier than quarrying or mining. The method consists essentially of bringing the natural brine into shallow ponds enclosed by low earth walls and allowing the Sun to evaporate the water. The deposited salt layers are then harvested. On the shores of the Dead Sea one may find disused solar pans that were dyked by ancient saltmakers. In China very old solar pans described in 1882 by the German geologist von Richthofen are still in operation at the saltwater swamps that lie in the great bend of the Yellow River. Operations similar to those described by von Richthofen provided salt for Iran's important Isfahan district. In Africa , Timbuctu and Kano were supplied for thousands of years from Taodeni and Bilma.
A striking feature of salt swamps is the red colour caused by algae and bacteria multiplying in their stagnant water. The salt produced there is red, whereas quarried salt is grey and usually contains gypsum which gives it less flavour because of reduced solubility. The Madaba Map , dating from about 550 A.D. shows two ships sailing on the Dead Sea , one loaded with reddish salt from the old solar ponds and the other with grey salt from the quarry at Mt. Sodom.
The red brine
not only looks like blood but also tastes like it and makes a deep and
disturbing impression. The Bible indicates this in Kings II.3.22 "And
they rose up early in the morning and the Sun shone upon the water, and
the Moabites saw the water on the other side as red as blood. And they
said, "This is blood".
Airphoto of 'red' brines in static ponds
coloured by 'Dunaliella' algae
This passage probably refers to the red salt pans at Sodom. The old name "Sodom" for the southern end of the Dead Sea may be a contraction of the Hebrew words "sade" (meaning field) and "adom" (meaning red). That reddish salt was made there at the time of the Jewish uprising against Rome about 130 A.D. is proved by pieces of salt found by Yadin in a burial cave of the period . This salt corresponds in colour and size of crystal to what would be expected from careful crystallization from red brine on sticks.
It was the Chinese who about 400 A.D. conceived the modern idea of drilling deep into salt deposits and bringing up the brine for evaporation. They used bamboo pipes and some borings were as deep as 1000 meters. As fuel for evaporation they used coal, wood or natural gas .
SALTPETRE AND GUNPOWDER
THE EAST INDIA COMPANY
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MRBLOCH ARCHIVE, is researching the significance, of SALT [NaCl] through the period 1000 BC . up to the Industrial Revolution.
For detailed references of statements made here, or Bibliography- Please mail:
David Bloch - mblsalt@ibm.net.
MRBLOCH SALT ARCHIVE
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