Origins of Tarmac

Origins of Tarmac

‘Tarmac or ‘Tarmacadam’ was until recently the commonly preferred material used in road surfacing. But ‘Tarmac’ properly refers to a type of ‘tar penetrating macadam’ and was actually a product patented around 1901 by Henry Purnell Hooley. ‘Tarmac’ however has come to be used as a generic term like ‘Hoover’, for products which are not always even the same thing. People make references to ‘on the tarmac’ to include any flat road surface or aircraft runway which would have once been constructed of ‘tarmac’. Although Bituminous surfaces and tar grouted macadam are closer to the real thing, some modern surfaces (such as asphalt concrete) are far removed from real tarmac product. But for the purpose of this article and an examination of what tarmac really is we are only concerned with the real thing

tarmac Henry Purnell Hooley

Henry Purnell Hooley was born in 1860 in Swansea and died in 1942. He was the founder of what is now Tarmac PLC. He was an articled civil engineer in Bristol but went on to work in various surveying capacities with local authorities throughout England before settling at Nottinghamshire County Council in 1889 as County Surveyor. This position led him to apply his mind to inventing what we now know as ‘tarmac’. The revelation of ‘tarmac’ came on the road to somewhere in Nottinghamshire. Whilst passing a tarworks Mr Hooley noticed that a barrel of tar had spilled on the road and gravel had been spread on top of it to clear up the mess. He noticed that the area affected was free of dust as compared with the rest of the road around it. Mr Hooley considered the implications and in 1902 went on to register a patent for Tarmac. Tarmac’s patent number is GB7796. The product was (eventually) a huge success but the name (again eventually) given to it was a good one as well, something which couldn’t be said for the name of the company Mr Hooley founded. He called the company, which he registered a year later ‘Tar Macadam Purnell Hooley Patent Syndicate Ltd’. Hooley was not much of a businessman either and had no real success with his product. In 1904 Mr Hooley obtained another patent for the machine to prepare the tarmac. This new patent was granted for the snappily titled ‘an apparatus for the preparation of tar macadam’. Further lack of success ensued and in 1905 Hooley’s company was bought by Sir Alfred Hickman. Alfred Hickman was the Member of Parliament for Wolverhampton. It being an age in which it wasn’t frowned upon for politician or public servant to be good at something useful, Sir Alfred had already established  a steelworks which produced large amounts of slag that would otherwise go to waste. Sir Alfred re-launched the ‘tarmac’ company.

Tarmac in Babylon

In the 7th Century BC Babylon, which is now located in the centre of Iraq became the first city to pave its road surfaces with tar. Babylon had already been going for over a thousand years and tar covered streets were the latest of its innovations. Despite its pivotal role in the history of civilisation not a great deal is left of the historical archaeology of Babylon so it’s not entirely clear as how close their product came to the product we know as ‘tarmac’ today The city had the misfortune to be ‘reconstructed’ and ‘improved’ during Saddam Hussein’s enlightened reign, but the ‘reconstruction’ was put on top of the old remains. Basically new modern palaces and installations were placed on the old foundations and the archeology of antiquity buried altogether. Were that an insufficiently ruinous episode for the city, the Americans arrived in 2003 and to all an intents and purposes razed the city to the ground, turning it into a Military base. Since then the Americans have apologised and the intention now is to restore it. The work however will take decades. It is hoped that some of the archeological record has survived under the rubble and the various of layers of modernity the alternating dictators and liberators built on it and we will eventually discover how close to modern tarmac the Babylonians came. It does seem possible they advanced beyond a mere primitive tar covered surface. Tar is prone to melting in Iraqi heat

imgresTarmac in the UK

By the 19th Century a precursor of tarmac became available in the UK. It was however a product not much more technically advanced than what in known of he Babylonian one. Scottish Engineer and road builder John Loudon McAdam devised a method knows as macadamisation to build smooth road surfaces which would not be as muddy as the traditional soil ones. This largely involved the application of surface stones and so it was not until Mr Hooley’s method of binding the stones together with tar (originally coal tar) that the true tarmac as we know it arrived. Since then the process has developed further into more advanced forms of tarmac and more recently moved on further to surfaces which are not properly tarmac at all

Efforts to make old style ’macadam’ roads more stable and resilient had started in the early 1830 when Cassells Patent Lava Stone Works in Millwall, pioneered, ’Pitch Macadam’. This early ancestor of tarmac involved spreading the sub-grade with tar, putting a macadam layer over it and then over sealing the whole thing with a mixture of sand and tar. Another process known to be in use by the late 1880s was ‘Tar Grouting’ and involved strengthening the surface of an already ‘macadamised’ surface, spreading tar over it and re-compacting it. Basically however ‘tarmac’ and its predecessor processes developed closely with and to meet the requirements of, the car. Hence Tarmac’s rapid progress in the early years of the twentieth century Roads prior to Hooley were suitable for coaches, carriages and horses but threw up a great deal of dust. They were also subject to being washed away during heavy rain or at least suffering fatal erosion over time by the elements. With the advent of the car (let alone faster cars) earlier roads were wholly unsuitable as compared with tarmac roads

Hooleys method had been the great leap forward in achieving the ‘tarmac’ system proper. Hooley’s tarmac was created by mixing aggregate and tar in advance of laying and then compacting it into the surface with a steam roller. His is the tarmac system we use on our roads nowadays. Later on, the tarmac mix was modified by adding pitch, Portland cement, and resin. In recent years asphalt has replaced tar owing to its better temperature tolerances. Asphalt being a by product of petrol production makes it much easier to obtain and is cheap. Strictly speaking however, this is not tarmac. The old ‘macadam’ process itself lost its appeal owing to increases in the costs and lack of availability of manual labour but a similar ‘tar and chip’ method is now employed. The modern process is sometimes known as chip seal’ or BST (bituminous surface treatment). Although genuine tarmac is not common nowadays we typically refer to the airport runway as tarmac even though it isn’t and in particular we even refer to the area near airport terminals as the ’tarmac’ despite its usually having been made of concrete. At the time of writing Wick Airport in Caithness Scotland has one of the few real tarmac runways left.