Histories of the chemical industry often draw attention to the Glasgow based industrialist and chemist, Charles Mackintosh, and his use of tar distillates in the manufacture of rubberised materials. As is obvious from his name, Mackintosh has been credited with the invention of rubberised, and thus waterproof, clothing ‑ but Charles Mackintosh was much more than that. The son of a successful Scottish dye manufacturer he was to become one of the foremost chemical manufacturers of the late eighteenth century. His influence stretched far beyond Scotland ‑ he had many connections with industries in England and Europe and with bodies such as the Royal Ordnance
Mackintosh made a contract with Glasgow Gas Works in 1819 to buy their waste tar and ammoniacal liquor. He experimented with 'essential oil', for which he had no immediate use, and thought it might be useful as a solvent for caoutchouc (India rubber). In 1822 he patented a method of cementing two pieces of cloth together using rubber emulsified with coal tar spirits and this led him to establish a factory to make waterproof articles.
Mackintosh was in London in 1824 and approached the Chartered for 'coal tar spirit'. 'Crude’ naphtha was still sold to his company by the Chartered thirty years later. A Mackintosh coal tar refinery existed at one time between Mile End Road and Poplar Road. This location not easy to identify, particularly within the confines of St. Leonard's, Bromley, Parish, but it could refer to a site in the same area as the Dundonald/Birch works mentioned in a previous chapter.
Nothing is as straightforward as it seems and it may be that London tar distillers had more to do with the development of rubber clothing than those in Glasgow.
Thomas Hancock, who has been described as, 'the foremost rubber technologist in the world',was a secretive and evasive man whose relationship with Mackintosh has never really been explained. His works were slightly north of the Brick Lane gas works in what was then called Goswell Mews and later became the site of the, now derelict, Gordon's Gin distillery. Hancock said that Mackintosh was his partner. Indeed a statement made in court during a patent case against clearly said 'Mr. Hancock and his partners are the firm of Charles Mackintosh'. This could even be taken to mean that Mackintosh was nothing at all to do with the company that bore his name
Mackintosh took out his patent for sandwiching together material to be proofed on 17th June 1823. This was narrowly preceded on 22nd March of the same year by a patent from Thomas Hancock on the use of coal tar naphtha as a solvent. Hancock did not claim however to have discovered the use this solvent for rubber but to have developed the way in which it was done. Neither Mackintosh nor Hancock claimed priority against the other and this might imply some sort of agreement between them.
Hancock himself described his experiments to find a suitable solvent and some of the problems he encountered. He developed a machine called a 'masticator' that enabled the rubber and solvent to be mixed in a particular way but this he did not patent. He then discovered that 'pitch and tar' were the best solvents he could find. He experimented with a number of distillates, which he obtained from Cassell in Poplar and decided that a wood tar distillate was best.
Both his process and Mackintosh's seem to have had some problems and Hancock obtained some sort of licence from Mackintosh. From that time Mackintosh and Hancock worked very closely together, and a large manufacturing base in Manchester was set up to work under Mackintosh's patent. This manufacturing base certainly had some connections with a gas works in the immediate area - and could have been the works of the Provincial Portable Gas Co. It is also worth noting that the London Portable Gas Co. was not so far distant from Thomas Hancock's Finsbury works.
Eventually Hancock began to develop a number manufactured goods from rubber using a range of different solvents according to need. He eventually achieved the hardening of rubber, which he called 'vulcanisation' ‑ there is also some suggestion of deathbed discussions with Mackintosh.
There were several Hancock brothers - one, John, managed Mackintosh's Manchester works. Another, Charles, was responsible for the processing of gutta percha and the subsequent breakthrough in cable making. The third brother, Walter, developed the most successful steam road vehicle of the period - and described his vehicles as running on 'common gas coke'. All four of these brothers had some connection with gas industry by products and all, except perhaps John, made some ground breaking contribution to industry and invention. It would be of great interest to know to what extent they worked together, or how far each one's contribution was individual.
Thomas Hancock had some contact with the early gas companies and is recorded as having bought spirits of tar from the Chartered Company in 1828. They took good care to check that he was a suitable person for them to deal with first - a great contrast to their treatment of Macintosh who appears to have been met with some deference.