By January 1879, at his laboratory in Menlo Park, New Jersey, Edison had built his first high resistance, incandescent electric light. It worked by passing electricity through a thin platinum filament in the glass vacuum bulb, which delayed the filament from melting. Still, the lamp only burned for a few short hours. In order to improve the bulb, Edison needed all the persistence he had learned years before in his basement laboratory. He tested thousands and thousands of other materials to use for the filament. He even thought about using tungsten, which is the metal used for light bulb filaments now, but he couldn’t work with it given the tools available at that time.
He tested the carbonized filaments of every plant imaginable, including bay wood, boxwood, hickory, cedar, flax, and bamboo. He even contacted biologists who sent him plant fibers from places in the tropics. Edison acknowledged that the work was tedious and very demanding, especially on his workers helping with the experiments. He always recognized the importance of hard work and determination. "Before I got through," he recalled, "I tested no fewer than 6,000 vegetable growths, and ransacked the world for the most suitable filament material."
Edison decided to try a carbonized cotton thread filament. When voltage was applied to the completed bulb, it began to radiate a soft orange glow. Just about fifteen hours later, the filament finally burned out. Further experimentation produced filaments that could burn longer and longer with each test. By the end of 1880, he had produced a 16-watt bulb that could last for 1500 hours and he began to market his new invention.
In Britain, Swan took Edison to court for patent infringement. Edison lost and as part of the settlement, Edison was forced to take Swan in as a partner in his British electric works. The company was called the Edison and Swan United Electric Company (later known as Ediswan which was then incorporated into Thorn Lighting Ltd). Eventually, Edison acquired all of Swan's interest in the company. Swan sold his United States patent rights to the Brush Electric Company in June 1882.