BitumenTwo with bitumen together glued stones of at least 36,000 years old are the oldest found bonding.
Bitumen is a viscous (sirup like) liquid that occurs naturally in crude oil. Having stepped distillation for recovering other components as naphtha, gasoline or diesel remains the most heavy substance left. Bitumen is an important component of asphalt.
It was used for bonding stone; and to seal tanks, boats, baskets waterproof.

Bitumen has to ambient temperature, the properties of a solid, but is physically a liquid. At higher temperatures, the fluidity is increasing.
Bitumen is also found under the ground, for example in Canada. Molten it is pumped or mined.

Tar and bitumen are strikingly similar but have different origins. Tar is obtained from coal or wood. Because of the high concentration of PAH (polycyclic aromatic hydrocarbons) is (coal) tar in road construction no longer applied since 1990.