Tar can be produced from corn stalks by heating in a microwave. This process is known as
pyrolysis.
A New Method of Macarony Making As Practiced at
Boston. Date made: 1830 Maker: Pendleton's Lithography; Johnston, David Claypoole Place: Boston, Massachusetts Description: Black and white print; outdoor scene of three men standing in front of a gallows with a broken rope hanging from the gallows. One man is tarred and feathered from from the neck down and has the other half of the broken rope around his neck.
Tar is a sticky black liquid made of thick oil. It is a natural substance, oozing out of the ground in places like the La Brea tar pits. Usually it is made by heating coal inside a chemical apparatus.
Most tar is produced from coal as a byproduct of coke production, but it can also be produced from petroleum, peat or wood. The "destructive distillation" of a ton of coal can produce 700 kg of coke, 100 litres of liquor ammonia, 50 litres of coal tar and 400 m3 of coal gas.
web | 
