In 1823, Charles Macintosh, a chemist from Glasgow, discovered that coal naphtha could dissolve natural rubber, leading to the invention of the modern raincoat. This discovery was based on industrial waste from gas works, specifically coal tar, which, when distilled, produced naphtha—a volatile and oily liquid. Macintosh, born in 1766, had left his position as a clerk before the age of 20 to study chemistry in Edinburgh under Joseph Black. He later focused on producing chemical products and bought byproducts from the city's gas works, including ammonia and tars. Macintosh's process involved creating a waterproof fabric by gluing two layers of fabric together with dissolved rubber. The first raincoats, however, had issues with stiffness in winter and stickiness in summer, which were later resolved by the vulcanization of rubber around 1839. Thomas Hancock improved upon Macintosh's formula by using crushed rubber that was richer and more consistent, resulting in a more effective waterproof coating. The patent for this method, filed in June 1823, was number 4804 and described a process that could be applied to various materials including hemp, flax, wool, cotton, silk, leather, and paper. The specification was drafted with the help of chemist William Hyde Wollaston. While Macintosh was not the first to explore the use of rubber for waterproofing, his process was the first to successfully create a practical waterproof fabric. Early raincoats had several flaws, including stiffness in cold weather and stickiness in warm conditions, as well as issues with seams allowing water to penetrate. These problems were addressed with the development of vulcanized rubber, which became available in 1839 and significantly improved the raincoat's performance. Macintosh's invention found early applications beyond clothing, such as waterproof canvas bags, pneumatic mattresses, and pillows for an Arctic expedition. A factory was opened in Manchester with financial support from the Birley house. Thomas Hancock obtained a license on the patent in 1825, leading to a collaboration with the Manchester firm. Hancock's use of recycled rubber led to a more consistent and effective waterproof coating. The two men merged their companies, and the collaboration resulted in the development of an automatic spreading machine that replaced the brushes used by Macintosh. In 1834, a fire destroyed Hancock's London factory, and Macintosh, who had already closed his Glasgow site, transferred all production to Manchester. The Manchester factory was later taken over by the North British Rubber Company. Macintosh died in 1843 near Glasgow at the age of 76. His name continues to be associated with raincoats, with the term "mackintosh" still used in British English to refer to the garment.