Charles Macintosh

Scottish chemist

• Born: December 29, 1766
• Birthplace: Glasgow, Scotland
• Died: July 25, 1843
• Place of death: Dunchattan, near Glasgow, Scotland

In 1823, Macintosh patented a waterproof fabric produced by spreading soluble rubber between two pieces of cloth. Using this fabric, he made mackintosh raincoats, an enterprise that continues today.

Primary field: Chemistry

Primary invention: Waterproof fabric

Early Life

Charles Macintosh (MAK-ihn-tosh) was born to the innovative Glasgow dye manufacturer George Macintosh and his wife, Mary Moore. Initially Macintosh worked as an accountant while he studied chemistry, first in Glasgow and later in Edinburgh under Joseph Black, a leader in practical, quantitative chemical analysis and a friend to James Watt, whose refinements to the steam engine had in 1769 inaugurated the Industrial Revolution. In 1786, at the age of nineteen, Macintosh abandoned accounting to devote his career to chemistry, chiefly in its application to the textile industry.

In his first year as a full-time chemist, Macintosh manufactured sal ammoniac (ammonium chloride) out of soot distilled from by-products of Glasgow’s new coal-gas works. This compound was used to produce alum, the mordant or astringent salt that made dyes color-fast for Glasgow’s expanding calico industry. Macintosh imported another mordant, sugar of lead (lead acetate), from the Netherlands, but he soon produced enough of that compound to export it to Rotterdam. He invented a chemical process for separating a third mordant, sulphate of alumina, from sulphate of lead. In 1790, he married Mary Fisher of Glasgow.

In 1792, Macintosh abandoned the sal ammoniac business, but the next year he developed a process of dyeing fancy muslin for the brand-new sewn-muslin industry in nearby Ayrshire. In 1795, Charles Tennant, a twenty-seven-year-old Ayrshire textile chemist, joined Macintosh to establish Scotland’s first alum works, using the aluminous shale readily available from coal waste in abandoned mines near Glasgow. Together, they invented a bleaching powder (chloride of lime), which Tennant patented in 1799. As a weaver, Tennant had noted how inefficient it was to bleach fabric by exposing it to stale urine under sunlight for months. Bleaching powder reduced the process to mere days, dramatically reducing the price of cloth and financially rewarding its inventors.

Life’s Work

In 1800, Tennant, Macintosh, and two additional partners established a chemical factory north of Glasgow, and Macintosh remained with the firm until 1814. His continued improvements to dyes included refinements of Prussian blue, a cheap substitute for indigo that produced a deep, durable shade, later called royal blue and associated with uniforms. Macintosh’s interests expanded beyond textiles. In 1809, he opened a yeast factory, although opposition from London brewers soon forced him to close it. In 1825, he patented a process for making steel by using a rush of coal gas to heat iron to a white hot, a technique that led Glasgow engineer James Beaumont Neilson to develop the hot blast furnace in 1828. Though Macintosh and Neilson’s invention proved essential to Scotland’s iron industry, fifteen years of patent litigation deprived both men of their profits. For his many contributions to British chemistry, Macintosh was elected a Fellow of the Royal Society in 1823, the year he patented his most famous product, waterproof fabric.

By his father’s death in 1807, Macintosh was running the family factory, manufacturing cudbear, a deep-red dye, from lichens soaked in ammonia water, and a decade later, he was experimenting with inexpensive ways to make Amazonian rubber soluble for practical use. Meanwhile, another Scottish-born inventor, William Murdoch, had employed coal gas for cheap artificial lighting. Piped through cities, the gas illuminated factories, theaters, and street lamps, but its production left two waste products: ammonia water and sticky, black coal tar oil. In 1819, Macintosh contracted with the Glasgow Gas Works to buy both. The ammonia supplied his cudbear operation, and from the coal tar oil, Macintosh distilled naphtha, which made rubber soluble. He brushed the rubber adhesive onto fabric and before the naphtha evaporated, fixed a second layer of fabric over it, thus making it repel water.

To produce waterproof garments on a commercial scale, Macintosh formed Charles Macintosh and Company in partnership with three leading cotton manufacturers in Manchester, England, where the company’s factory opened in 1825, powered by steam and lighted by coal gas. By supplying rainproof garments to the military as well as the public, the company succeeded despite problems with the product. Naphtha gave the fabric a disagreeable odor, and even in Britain’s temperate climate, rubberized fabrics turned stiff in the cold and soft in the heat. Moreover, water penetrated the holes left by tailors’ needles, and fitted rubberized garments did not allow their wearers’ perspiration to escape. The man to solve these difficulties was a Londoner, Thomas Hancock.

Twenty years younger than Macintosh, Hancock had also begun in 1819 to experiment with rubber garments and in 1820 had patented elastic wristbands and garters. Around 1821, he perfected the masticator, a machine that tore and heated rubber scraps into a solid mass that could be rolled to specified thicknesses. In 1825, licensed by Macintosh to manufacture rainwear, he reduced the naphtha odor, and his brisk sales threatened Macintosh’s dominance of the industry. By 1830, Macintosh had negotiated with Hancock to supply his company with rubberized fabric, and in 1834, Hancock became a partner in the company and assumed control. He replaced irregular rubber application brushes with a uniform mechanical spreader, designed loosely fitted raincoats for comfortable air circulation, and hired company tailors, supervising their stitching and replacing those who pierced cloth excessively.

In 1838, a fatal fire swept the Manchester factory while Hancock was visiting Macintosh in his Glasgow retirement. Hancock hurried south to supervise the cleanup, and by 1840, an expanded Manchester operation was producing more than three thousand square yards of rubberized fabric a day. Shortly after Macintosh’s death in 1843, Hancock solved the last problem with rubberized cloth when he patented the vulcanization process, which weatherproofed rubber by pressure-heating it with sulfur. Although Hancock scrupulously documented his chemical research, he concealed the source of the vulcanized rubber samples that had inspired him, the American inventor Charles Goodyear, who had held the U.S. patent since 1839.

Macintosh died in 1843 at home at Dunchattan, the estate his father had built near Glasgow for his cudbear factory. Hancock expanded Charles Macintosh and Company into the world’s largest manufacturer of rubber goods while he immortalized—and altered the spelling of—the founder’s name as a synonym for raingear.

Impact

Under Hancock’s management, Macintosh and Company expanded its product line to include almost all modern uses for vulcanized rubber except inflated tires. Inflatable beds, pillows, and cushions assisted invalids and rail travelers. Surgeons used rubber tubes, sheeting, and bandages. Brewers and distillers used rubberized hose after learning how to preserve the flavors of their goods. The company supplied the military with not only waterproof capes, saddle covers, and cartridge covers but also tubes for sea divers. Pontoon boats, life preservers, hot-water bottles, and rubber boots served military and civilian needs. Inflexible rubber, called ebonite, anticipated plastic.

Charles Macintosh and Company staged award-winning displays of useful rubberized inventions at London’s Great Exhibition of 1851 and the Paris Exhibition of 1855.

In 1857, Hancock noted that between 1842 and 1855, rubber imports in the United Kingdom rose from 140 tons to 2,235 tons. These exports, however, came at a cost to the native rubber workers in South America and in the new plantations of colonial Malaysia and the Congo. Modern historians estimate that in the years before World War I, the Amazon rubber industry claimed a native life for every 330 pounds of rubber it produced, while in the Congo, a native died for every 22 pounds of rubber. Public outcry and the invention of synthetic rubber have dramatically decreased the death count, even as rubber production continues to rise. In 2005, world production was 6.5 million tons of natural rubber and 8.7 million tons of synthetic rubber.

The company started by Macintosh has become Mackintosh Ltd., a Glasgow-based global company, with distributors across Europe and in North America and Japan. It markets high-end rainwear in traditional and fashionable styles to men and women using technological innovation and brand loyalty.

Bibliography

Loadman, John. Tears of the Tree: The Story of Rubber. New York: Oxford University Press, 2005. Details how the rising demand for raw rubber led to brutal slave labor in South America and the Congo. Examines how synthetic rubber and creative recycling multiply rubber’s uses. Illustrations, index, bibliography, time line.

Müller, Ingo, and Peter Strehlow. Rubber and Rubber Balloons: Paradigms of Thermodynamics. New York: Springer-Verlag, 2004. A history of the European discovery of rubber, including how Joseph Priestley named it for its use in rubbing out pencil marks. Detailed molecular analysis of rubber’s elasticity. Index, diagrams.

Schoeser, Mary. World Textiles: A Concise History. New York: Thames and Hudson, 2003. Describes Macintosh’s invention and commercial implementations of bleaches, dyes, mordants, and rubberizing but does not identify him by name. Color illustrations, indexes, bibliography, glossary.

Slack, Charles. Noble Obsession. New York: Hyperion, 2002. Examines the career of Hancock. Slack feels Hancock’s failure to acknowledge Charles Goodyear’s contributions are a blemish on an otherwise admirable career. Illustrations, index, bibliography.