Tar is a dark brown or black viscous liquid made by heating coal, wood, peat or another carbon-rich material in the absence of air, a process called destructive distillation. It is not the same thing as bitumen, which is the heavy residue of crude oil refining, or asphalt, which in British usage is the road mix of bitumen and stone. Most of what people call "tar" on a modern road or roof is bitumen.
The three words are mixed up in everyday speech and in trade enquiries. A buyer who asks for "road tar" almost always needs bitumen. A buyer who asks for coal tar needs a different product, from a different industry, shipped under different rules.
What is tar?
Tar is a manufactured product. When coal or wood is heated without air it breaks down into gas, a solid residue (coke or charcoal) and a condensed liquid. That liquid is tar.
- Coal tar is a by-product of making coke and coal gas from coal. Most of it now comes from the coke ovens that serve iron and steel works.
- Wood tar comes from the dry distillation of wood, traditionally pine. It was used for centuries to seal the hulls of wooden ships and boats.
Coal tar is a chemical feedstock more than a construction material. It contains polycyclic aromatic hydrocarbons with two to seven rings, such as naphthalene, together with phenols and benzene, toluene and xylenes. It is distilled into oils and coal tar pitch, and the pitch is used in carbon electrodes for aluminium smelting. As of 2011 about 30 million tons of coal tar were produced a year, and roughly half went to chemical production. The products are covered on our coal tar products pages, including crude coal tar and coal tar pitch.
What is bitumen?
Bitumen is the heaviest fraction of crude oil. A refinery distils crude at atmospheric pressure and then under vacuum; the material that boils above roughly 500°C stays at the bottom of the vacuum column, and that residue is bitumen. It also occurs naturally, for example at the Pitch Lake in Trinidad.
Bitumen is a binder. About 85% of the bitumen used worldwide goes into road surfacing and about 10% into roofing. Our guide What is bitumen? covers the grades and how it is made.
What is asphalt?
This depends on where you are.
- In American English, "asphalt" is the binder itself, the material the rest of the world calls bitumen. US engineers say "asphalt binder" or "asphalt cement" when they need to be exact.
- In British English, "asphalt" is the finished paving mix: crushed stone, sand and filler bound with bitumen. The US name for that mix is "asphalt concrete", "hot mix asphalt" or simply "blacktop".
A typical road mix is about 5% bitumen and 95% aggregate by weight. So a British contractor who orders asphalt receives a hot stone mix from a plant, and an American buyer who orders asphalt may mean the liquid binder in a heated tanker. In a trade enquiry the grade settles it: a penetration grade such as 60/70 or a performance grade such as PG 58-22 is the binder.
Bitumen vs tar: what is the difference?
They look alike and behave alike when hot, but they come from different raw materials and have different chemistry.
| Tar (coal tar) | Bitumen (US: asphalt) | Asphalt (UK sense) | |
|---|---|---|---|
| What it is | Condensed liquid from heating coal without air | Vacuum residue of crude oil refining | Paving mix of aggregate and bitumen |
| Raw material | Coal (also wood or peat for other tars) | Crude oil | Stone, sand, filler, about 5% bitumen |
| Made at | Coke ovens, formerly gasworks | Oil refineries | Asphalt mixing plants |
| Main use today | Chemical feedstock, pitch for electrodes | Road binder, roofing, waterproofing | Road, runway and car park surfacing |
| Health classification | Coal tars are IARC Group 1 carcinogens | Not a coal tar product | Depends on the binder |
| Used in new roads | No, largely replaced since the 1970s | Yes | Yes |
Tar vs asphalt: why did tar leave road building?
Tar came first. In 1902 the English surveyor Edgar Purnell Hooley patented a method of mixing tar with aggregate and compacting it with a steamroller. In 1903 he formed the Tar Macadam Syndicate and registered "tarmac" as a trademark. The name outlived the material.
Two things pushed tar out. As oil refining grew, bitumen became plentiful and took over as the standard binder. Then the health evidence caught up: the International Agency for Research on Cancer lists coal tars as Group 1 carcinogens. Bitumen has largely replaced coal tar in road applications since the 1970s.
Coal tar survives in some pavement sealcoats, which typically contain 20 to 35% coal tar pitch, and these are now restricted too. Several US cities and states have banned them, and Canada has banned coal tar in sealants from 2025.
In British speech "tarmac" now simply means an asphalt surface, and people still say a road is being "tarred". The binder in both cases is bitumen.
Is tar flammable?
Yes. Tar is a hydrocarbon material and it burns. How easily it ignites depends on the fraction.
- Light coal tar oils, the low-boiling liquids distilled out of coal tar, are highly flammable. The US NOAA chemical datasheet for coal tar light oil gives a flash point of 60 to 77°F, which is about 16 to 25°C, so the vapour can ignite at room temperature.
- Crude coal tar and pitch are far less volatile. They are combustible, and coal tar is classed as a dangerous good for transport under UN number 1999.
- Bitumen, the "tar" of roofing and road work, is stored and shipped hot, at around 150°C. The practical hazards are burns from the hot liquid and fire if it is overheated or if a light solvent has been blended in, as in cutback grades.
For any cargo, the safety data sheet from the producer states the flash point of that product, and that is the figure to work from.
Which word to use in an enquiry
- For road binder, write bitumen and the grade, for example bitumen 60/70, or the American equivalent, asphalt binder with a PG grade.
- For roofing and waterproofing grades, write oxidised bitumen.
- For the coke-oven product, write coal tar or coal tar pitch and state the softening point and intended use.
- Avoid "tar" on its own. A seller cannot tell which of the three you mean.
How these products are traded
Bitumen moves in bulk in heated tankers, and in steel drums or bags inside containers for destinations without a heated terminal. Coal tar and its pitch move in tankers, ISO tanks or as solid pitch, under dangerous goods rules.
CBIL is a commodity brokerage company. We broker cargo between a named refinery or seller and a named buyer, on FOB, CFR or CIF terms, against independent inspection by SGS, Intertek or a similar company at loading. The inspector's certificate of quality and quantity is a contract document.
Request a bitumen quote with the grade, quantity, packing and destination port.