I - 24 : Tar - More than just Pitch Black

Tar has a high Viscosity and flows slowly but is still liquid at Room Termperature

There are many unsung innovations in history. One of them is Tar. In the ancient world it protected wood against insects, made ships water proof, ropes resistant to rot, sails able to catch wind, it greased door hinges, was used for torches, as every day glue and applied to skin diseases.  In the middle ages it was also used to caulking ships and shaming people – the famous “tar and feathering”.

The Olympias, the Trireme Replica, was waterproofed with Pine Tar hence the brown colour

Tar’s most important role was probably in the development of maritime trade and naval warfare. In antiquity, the hulls of ships were built first before being strengthened with inner ribs. When the planks were wet, they became watertight. In the water, they were exposed to shipworms and barnacles though which could consume the wood within a few years. Tar was applied to protect the hulls. At least once a year, ships were lifted from the water and repainted. At the same time, planks that suffered from worm infestation were replaced. Thus the lifespan of antique ships could be extended to decades.

Built in 2008, this Replica of a Phoenician Merchant Vessel sailed around Africa - According to Herodotus, the ancient Historian, the Phoenicians did this already in 600 BC

For the Phoenicians ship rot was less a problem. Lebanon cedars are naturally worm and insect resistant. They needed tar only for the oak keel, the masts, ropes and sails. Flax textiles are not wind proof – too much air passes through them and makes them inefficient for propulsion. By soaking sails repeatedly in tar the problem is solved. Tar remains viscous for a long time and gives the sails the flexible coating need. Protecting ropes from rot was equally important. Hemp – when wet – is an ideal host for mould which feeds on the fibers. If not dried, mould quickly weakens the strength. But ropes on a ship are always wet. Tar again resolves the issue.

Traditional Taring Method Replication for Ropes

Could not find out how tar was actually invented. People in Mesopotamia and Syria did not need it since there was natural tar from open oil pits on the surface. Oil based tar was used in Mesopotamia for millennia. I guess the Phoenicians used such tar on their ships. Making tar from cedar trees is possible but laborious and time consuming. Oil-based tar was near-by and free. This conclusion is speculative from my part and would require more research than I have time for. But it makes sense to me.

Anybody can make Tar - all you need is Fat Wood (=lots of raisin), a Pot, a Pipe and Fire

Greek and later Romans did not have it so easy. They had to “invent” tar. Luckily, tar is a natural biproduct of wood fire. It works by depolymerising biomass (breakdown of cell membranes and lignin) when the fire burns between 200 and 500 degrees Celsius. At this temperature, part of the biomass turn into primary tar, also known as wood syrup. It contains a mixture of  phenol, guaiacol, veratrole, fatty acids etc. I know – it is a while that we took chemistry classes. Pine trees with their elevated raisin levels are ideal for cooking tar. The Romans thought pine tar was the best for ships. They also imported birch tar from Germany and Scandinavia which was used as glue. Birch tar was far more expensive than pine tar and a luxury good for the Roman elite.

Diagram of Ancient Tar Cooking in the Open Woods

Later in naval history, tar was also used for caulking ships. Once canons were mounted on ships in the 15th century, the hull and deck planks got thicker to provide platform stability and protect the ship from canon balls. The gaps between the “fat” planks had to be sealed with oakum which was hammered between them and then drizzled with tar to perfect the seal. Once dried, the excess tar was cut away with a sharp knife. Thin black lines and large planks neatly altered. A design we still see on the decks of modern sail boats. They are of decorative nature though - the black lines are made of silicon not tar anymore.

Caulking the Golden Hind, Sir Francis Drakes ship now mored in the River Thames in London

Do not want to close this blog without talking about the medical use of tar. Liquid at room temperature it was applied to healing skin rashes and other skin infections. Tar is sticky for a while but eventually washes off. This later property was used for the “Tarring & Feathering” a procedure used to shame people for crimes committed or other "sins". The feathers would stick for a good day - the tar wash off within a week. Tar was not “invented” for this purpose though. But it is amazing how "creative" the human mind is.

Two Bostonians Tarring & Feathering an English

Custom Officer forcing him to dring imported Tea

Below the link to a YouTube video on how to make tar:    

 https://youtu.be/nEV6GXViVHo?si=3GhTcmGGWqjyOZOb