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Sylvia Rose

Bitumen - Tarry Trade in Perfect Pitch

Bitumen, a natural petroleum product, is a common trade route item in the ancient world. The earliest known use of bitumen dates back to 40,000 years ago, to the Paleolithic Age. Thick and sticky, liquid bitumen is used to fix handles on stone tools like axes and hammers.


Read: Cult of the Fire God - Bronze Age Adventure New 2024


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bitumen, a black tarry substance
Dead Sea Bitumen, solid form

Easy to harvest from the Earth's surface and natural pools, bitumen has a strong history of trade, building, toolmaking and everyday use. A viscous constituent of petroleum, bitumen is found in black sticky liquid form, or in a solid mass.


Read: Cult of the Fire God - Bronze Age Adventure New 2024


In the US it's commonly called asphalt. Elsewhere, the difference between asphalt and bitumen is that bitumen is a naturally occurring substance, while asphalt is a mixture of bitumen, gravel and sand.


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asphalt with gravel
Asphalt made with gravel

The word asphalt derives from the ancient Greek ἄσφαλτος ásphaltos, referring to natural bitumen or pitch. Before the 20th century bitumen is sometimes called asphaltum. Bitumen can also be synthetically refined from petroleum.


Likewise tar and pitch, terminology often used interchangeably, are products of a distillation process at high heat. Production of wood coal creates tar as a byproduct. Tar kilns found at sites like Indus Valley and later are used to produce tar from coal, wood, petroleum or peat.


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wood burns in furnace
High heat is needed

Evidence of bitumen for waterproofing goes back to c. 5000 BCE. A crop storage basket discovered in Mehrgarh, of the Indus Valley civilization, is lined with bitumen. Bitumen travels along trade routes of Egypt, Greece and Europe, Mesopotamia and the Jade Roads.


Read: Cult of the Fire God - Bronze Age Adventure New 2024


By the 3rd millennium BCE refined rock asphalt is in use in the Indus Valley region. It's used to waterproof the 'Great Bath' in Mohenjo-daro, an ancient city established c. 2500 BCE. The city is abandoned in c. 1700 BCE due to sudden decline of the Indus Valley civilization.


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Mohenjo daro, a town of the Indus Valley civilization, excavations
Excavations at ancient Indus Valley city Mohenjo-daro

Bitumen is used in the construction of the legendary 1 kilometer (0.62 mi) long Euphrates Tunnel. Said to be built between c. 2180 and 2160 BCE, it was created from burnt bricks covered with bitumen for waterproofing.


The tunnel reportedly ran under the Euphrates river, uniting the two parts of Babylon. It's described to have been about 3.6 m (12 ft) high and 4.6 m (15 ft) wide.


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person walking into tunnel
A tunnel of legend is said to have run beneath the Euphrates at Babylon

In the ancient Near East, Sumerians use natural bitumen deposits as mortar, to cement parts of carvings, such as eyes, for ship caulking and basic waterproofing. Greek historian Herodotus (c. 484 - 425 BCE) describes hot bitumen used as mortar in the walls of Babylon.


Along with animal fats, beeswax, myrrh, pistachio resin, cinnamon and plant oils, bitumen is used by ancient Egyptians to embalm mummies. No quantity larger than 45% is found in the mix.


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person in bandages on head with lip brush
Self-embalming mummy

Bitumen continues to be a valuable strategic resource in the age of antiquity. It's the cause of the first known battle for a hydrocarbon deposit, which occurs between the Seleucids, a major Hellenistic culture, and Nabateans, people in North Syria and the Levant in 312 BC.


The major source of bitumen for the Egyptians is the Dead Sea, which Romans call Palus Asphaltites (Asphalt Lake). In approximately 40 AD, Dioscorides describes the Dead Sea substance as Judaicum bitumen.


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Dead Sea and shoreline
Dead Sea landscape - also known for salt

Sidon bitumen is thought to refer to bitumen from Hasbeya, Lebanon. Pliny mentions bitumen being found in Epirus, an Aegean Greek coastal region.


In the ancient Far East, natural bitumen is processed by slow boiling. The melting point of bitumen is around 120 -150°C (248 - 302°F). Evaporation leaves a thermoplastic of higher molecular weight, so it hardens when cool.


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viscosity of bitumen
Experiment showing the viscosity of bitumen

Applied in layers, it's used to cover scabbards, bags, baskets and other objects to waterproof them. In the East, figurines of household deities are cast with the processed bitumen.


In various regions, tar kilns are used to collect the sticky substance while making coal. A tar kiln is a pit in the ground, with a barrel inside to catch the tar.


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tar kiln
Tar kiln in Sweden (photo: Svenboatbuilder)

The pit is filled with pine or other resinous wood, known as lightwood, and covered with earth. As the wood burns, tar runs out into the barrel.


Bituminous coal, or black coal, is a type of coal containing bitumen. A medium quality coal, it can be black or dark brown. It often has a banded or layered structure.


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black bituminous coal
Bituminous coal

Effects of working with bitumen can be deadly, especially in the ancient world when the hazards of many materials aren't well known. Arsenic is another example, as arsenic is at first used instead of tin to make bronze.


In Canada, aboriginal people use bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes. They also heat it in smudge pots to repel mosquitoes and blackflies in spring and summer.


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big mosquito on leaf
Mosquitoes - part of summer life

The largest natural deposit of bitumen in the world, estimated to contain 10 million tons, is the Pitch Lake of southwest Trinidad. In 1595 CE explorer Sir Walter Raleigh makes use of the resources to caulk his ship. He describes the pitch as


" ... most excellent ... It melteth not with the sun as the pitch of Norway."

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