Raincoats
This invention, patented more than 180 years ago, insures you’ll be well protected against April showers.
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Although Macintosh is considered the father of the raincoat−waterproof coats are still called mackintoshes in the U.K.−he was by no means the first to try to make water-resistant fabrics. As early as the 13th century, South American natives were coating cloth with natural liquid latex to make waterproof footwear and capes.
What would-be waterproofers needed was a good solvent for making latexlike solutions with solid rubber. In 1748, French scientist François Fresneau devised a way to waterproof fabric based on the natives’ techniques using turpentine as a rubber solvent. About 70 years later, Scottish surgeon James Syme, a contemporary of Macintosh’s, found that the hydrocarbon mix known as coal tar naphtha readily dissolved rubber and could be used for waterproofing. Syme wasn’t interested in commercializing this discovery, however.
Coal tar naphtha was one of the waste products from the conversion of coal into the gas used in streetlamps. Macintosh had a contract with the Glasgow Gas Light Co. to buy the waste products from this process. Principally, he was interested in extracting ammonia from this waste for his father’s dye business. But he was still left with an abundance of coal tar naphtha.
Macintosh soon learned of coal tar naphtha’s rubber-dissolving properties, and he found that fabric treated with this solution became waterproof. The fabric was sticky, though, and it had a foul smell. “Macintosh’s brilliant idea to avoid the stickiness was simply to press two sheets of fabric together with the rubber sandwiched between them,” Loadman says. “Unfortunately, the smell remained.”
Macintosh patented the invention in 1823; however, it was anything but an instant success. The smell put most people off, and Macintosh’s customer service skills were decidedly lacking. Sizable and steady demand from the armed forces and merchant navy was all that kept Macintosh’s waterproof fabric business afloat. “I should imagine that the waterproofing properties more than compensated for one extra smell amongst many that the soldiers and sailors would be experiencing,” Loadman jokes.
Visit “What’s That Stuff” to continue reading about the chemistry of raincoats.
Excerpted with permission, Chemical & Engineering News
Copyright © 2006 American Chemical Society