yeast technologist

SUBJECT AREA: Chemical technology, Textiles

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As the son of the well-known and inventive dyer George Macintosh, Charles had an early interest in chemistry. At the age of 19 he gave up his work as a clerk with a Glasgow merchant to manufacture sal ammoniac (ammonium chloride) and developed new processes in dyeing. In 1797 he started the first Scottish alum works, finding the alum in waste shale from coal mines. His first works was at Hurlet, Renfrewshire, and was followed later by others. He then formed a partnership with Charles Tennant, the proprietor of a chemical works at St Rollox, near Glasgow, and sold "lime bleaching liquor" made with chlorine and milk of lime from their bleach works at Darnley. A year later the use of dry lime to make bleaching powder, a process worked out by Macintosh, was patented. Macintosh remained associated with Tennant's St Rollox chemical works until 1814. During this time, in 1809, he had set up a yeast factory, but it failed because of opposition from the London brewers.

There was a steady demand for the ammonia that gas works produced, but the tar was often looked upon as an inconvenient waste product. Macintosh bought all the ammonia and tar that the Glasgow works produced, using the ammonia in his establishment to produce cudbear, a dyestuff extracted from various lichens. Cudbear could be used with appropriate mordants to make shades from pink to blue. The tar could be distilled to produce naphtha, which was used as a flare. Macintosh also became interested in ironmaking. In 1825 he took out a patent for converting malleable iron into steel by taking it to white heat in a current of gas with a carbon content, such as coal gas. However, the process was not commercially successful because of the difficulty keeping the furnace gas-tight. In 1828 he assisted J.B. Neilson in bringing hot blast into use in blast furnaces; Neilson assigned Macintosh a share in the patent, which was of dubious benefit as it involved him in the tortuous litigation that surrounded the patent until 1843.

In June 1823, as a result of experiments into the possible uses of naphtha obtained as a by-product of the distillation of coal tar, Macintosh patented his process for waterproofing fabric. This comprised dissolving rubber in naphtha and applying the solution to two pieces of cloth which were afterwards pressed together to form an impermeable compound fabric. After an experimental period in Glasgow, Macintosh commenced manufacture in Manchester, where he formed a partnership with H.H.Birley, B.Kirk and R.W.Barton. Birley was a cotton spinner and weaver and was looking for ways to extend the output of his cloth. He was amongst the first to light his mills with gas, so he shared a common interest with Macintosh.

New buildings were erected for the production of waterproof cloth in 1824–5, but there were considerable teething troubles with the process, particularly in the spreading of the rubber solution onto the cloth. Peter Ewart helped to install the machinery, including a steam engine supplied by Boulton \& Watt, and the naphtha was supplied from Macintosh's works in Glasgow. It seems that the process was still giving difficulties when Thomas Hancock, the foremost rubber technologist of that time, became involved in 1830 and was made a partner in 1834. By 1836 the waterproof coat was being called a "mackintosh" [sic] and was gaining such popularity that the Manchester business was expanded with additional premises. Macintosh's business was gradually enlarged to include many other kinds of indiarubber products, such as rubber shoes and cushions.

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