After serving as a pharmacist's apprentice, Swan became a partner in a chemical firm that manufactured photographic plates. At that time, one of the mostdifficult steps in the production of photographic plates involved adding chemicals in a liquid state to the plates. However, Swan discovered that the fluids used on the plates became more sensitive when carefully heated. This meantthat the plate could actually work better when dry. By 1871, Swan had developed the much simpler "dry-plate" photographic method. His innovation initiated a new era in photography, leading to rapid improvements over the next 20 years. Swan also invented the first bromide paper, which is still widely used for printing photos.
Swan's primary interest, however, was electric light. Recalling the days of his youth, when indoor lighting was dim and expensive, Swan observed that "asa rule, the common people went to bed soon after sunset." Swan began to experiment with incandescent filaments while in his twenties. He came across a patent on an incandescent lamp in the name of J. W. Starr (1822-1847), an American who had died at age twenty-five before he could fully develop his idea. Although Starr's lamp used a platinum filament, he had noted that in a vacuum,carbon could be used. By 1860, Swan succeeded in making filaments with stripsof carbonized paper, but his lamps remained impractical for two reasons: vacuum pumps at the time were unable to create a high enough vacuum to protect the carbon filament and electricity supplied by batteries was expensive and unstable.
Swan abandoned this research for 17 years. Then in the late 1870s, he read about the work of William Crookes, who was analyzing new gases, and learned that Hermann Johann Philipp Sprengel had invented a more effective vacuum pump.Also, power generators called dynamos had been improved to the point where they could supply cheaper, more reliable electricity than batteries. Soon Swanhad invented a practical incandescent filament lamp, which he displayed in December 1878. His own house was the first electrically illuminated private home in England. In 1881, Swan formed a company to manufacture his "glow lamps,"and they quickly became popular in England. By the early 1880s, they were installed in the Savoy Theater, the House of Commons, and the British Museum. At one point, Swan's factory received an order from the United States for 25,000 lamps.
Meanwhile, Thomas Alva Edison had begun similar research and had aggressivelyprotected his work with patents. In 1882, Edison sued Swan for patent infringement. When Edison's lawsuit failed to stop work at Swan's factory, the twoinventors settled out of court, joining forces in 1883 to form the United Electric Light Company. Swan continued to improve incandescent filaments and, asan offshoot of his research, created what was to become the first syntheticfiber when he developed a method for making fine threads out of nitrocellulose, which could be converted to less flammable cellulosefibers. The French chemist Louis Comte de Chardonnet adapted Swan's process to produce artificial silk, later named rayon. In recognition of his scientific contributions, Swanwas knighted in 1904.