Charles Macintosh

Two men named Macintosh gave Glasgow to the world, and they are forever confused. This one is not Charles Rennie Mackintosh the architect, born two generations later, but Charles Macintosh the chemist — the man who gave the rainy world the garment that still bears his name. A Glasgow dyer’s son, he was hunting for some useful purpose for the sticky black waste of the city’s new gasworks when he found that it would dissolve rubber; and so, in 1823, he patented the waterproof cloth that became the ‘mackintosh’, complete with a stray and unexplained letter ‘k’.

This page tells his story: his origins in the dye trade, his career as a Glasgow chemist, his partnership with Charles Tennant, the gasworks waste that inspired him, his famous invention, the raincoat that took his name, and his wider work.

The dyer’s son

Charles Macintosh was born in Glasgow on 29 December 1766, the son of George Macintosh, a manufacturer who ran a works producing cudbear — a violet-red dye extracted from lichens, used to colour wool and silk. The boy grew up, then, surrounded by the chemistry of colour, in a city whose fortunes were increasingly bound to the dyeing and printing of cloth. He began his working life as a clerk, but chemistry was his passion, and he pursued it in earnest, attending the celebrated lectures of Joseph Black, the discoverer of carbon dioxide. Before he was twenty he had abandoned the counting-house for the laboratory, and set out to make his living from the new industrial chemistry.

A Glasgow chemist

Macintosh proved a gifted and enterprising chemist. In 1786, still only nineteen, he opened his own chemical works, manufacturing such useful substances as sal ammoniac and the pigment Prussian blue; in 1797 he established the first alum works in Scotland. Much of his early work served the great local trade in printed cotton, or calico, supplying the mordants and dyes on which the colouring of cloth depended; in time he inherited and ran his father’s cudbear business as well. He was, in short, exactly the kind of practical, inventive man of science on whom Glasgow’s booming textile industry depended, turning the discoveries of the laboratory into the processes of the factory that drove the Industrial Revolution.

Bleaching powder & Charles Tennant

One of his most important ventures was a partnership with a fellow chemist, Charles Tennant. Together, around the turn of the century, they perfected a solid bleaching powder — a dry, stable chemical that could whiten cloth and paper far more quickly and cheaply than the old method of laying linen out in fields to bleach in the sun. Manufactured at Tennant’s great St Rollox works in Glasgow, which grew into the largest chemical factory in the world, this bleaching powder transformed the textile and paper trades, and remained in industrial use well into the twentieth century. It was a formidable achievement in its own right — yet it is not the invention for which Macintosh is remembered.

The waste of the gasworks

That came from rubbish. In 1818 a gasworks opened in Glasgow, piping coal gas through the city to light its streets and factories; but the making of the gas left behind troublesome waste products, among them quantities of sticky coal tar. Macintosh, ever alert to turning waste into wealth, set about finding uses for it. From the tar he distilled naphtha, a volatile, oily liquid, and from 1819 he experimented tirelessly to find some profitable purpose for it. In doing so he stumbled upon a curious and valuable property: naphtha, he discovered, would dissolve india-rubber, the natural rubber recently arrived from South America, turning it into a soft, spreadable solution.

The waterproof cloth

From that discovery came his masterstroke. Macintosh reasoned that if he painted this rubber solution onto cloth, the rubber, once the naphtha had evaporated, would leave the fabric coated and waterproof. The single layer proved sticky and unpleasant; so instead he spread the rubber solution on one piece of cloth and pressed a second piece on top, sandwiching the waterproof rubber between two layers of fabric. The result was a supple, wearable, genuinely water-repellent textile — and in June 1823 he took out a patent for the process, by which cloth of wool, cotton, linen and other materials could be rendered impervious to water. It was not the first attempt at waterproofing, but it was the first suited to manufacture on a large scale.

The ‘mackintosh’

The obvious use for such a cloth was rainwear, and coats made from Macintosh’s fabric soon became known by his name — the ‘mackintosh’, or simply the ‘mac’, in which an extra letter ‘k’ crept in, for reasons no one has ever satisfactorily explained. To manufacture the garments he founded the firm of Charles Macintosh and Company, later moving production to Manchester in partnership with cotton manufacturers there. The early coats had their faults — the rubber grew stiff in the cold and sticky in the heat, and tailors disliked working the material — but these were overcome in time, especially once rubber could be vulcanised, and the mackintosh became a fixture of British life. In the year of his patent, 1823, Macintosh was elected a Fellow of the Royal Society, in recognition of his standing as a chemist.

The wider chemist

The raincoat has rather overshadowed the rest of a busy and inventive career. Macintosh took out a patent for a method of converting iron into steel, and he assisted the ironmaster James Beaumont Neilson in perfecting the hot-blast process of smelting — an innovation that transformed the iron industry and Scottish heavy industry with it. To the end of his life he kept abreast of his science, still attending chemistry lectures at the university in his old age. He died at Dunchattan, then just outside Glasgow, in 1843. Today his name is spoken far more often than it is recognised: every ‘mac’ worn against a Scottish downpour is a memorial to the Glasgow chemist — not the architect — who first made cloth keep out the rain.

A life in dates