Electric Light Bulb Perfected

Electric Light Bulb Perfected

On October 21, 1879, Thomas Edison and his associates in Menlo Park, New Jersey, tested an incandescent light bulb that burned for a recorded 13 and a half hours. Their experiment demonstrated the feasibility of electric lighting and thus marked the beginning of a new era.

Edison was not the first to try to devise an electric light bulb. During the half century preceding his achievement, scientists throughout the world had attempted to develop a practical technique for electric lighting. Experiments in Great Britain, Russia, and the United States led to devices that utilized platinum or carbon conductors enclosed in glass globes or tubes. However, the results were disappointing, since these early incandescent light bulbs burned for only a few moments.

Edison briefly experimented with electric lighting in 1876 and again in 1877, but both times he abandoned the project without making any significant advances. In 1878, however, his interest in electric lighting revived. He felt frustrated with the work on the phonograph that had been occupying his attention, and he later recalled, “Just at that time I wanted to take up something new.” With the encouragement of Grosvenor P. Lowrey, the general counsel for Western Union, and Professor George F. Barker of the University of Pennsylvania, Edison launched the research project that ultimately produced one of the world's greatest inventions.

Before beginning his own experiments, Edison carefully studied the work of others. He also traveled to Ansonia, Connecticut, in September 1878 to see a display of electric arc lights. The exhibit greatly impressed Edison, but it did not convince him of the utility of the arc light, and he commented to his host William Wallace that “I believe I can beat you making the electric light. I do not think you are working in the right direction.”

Late in the autumn of 1878, Edison gave a press interview during which he made public his intention to devise an electrical system capable of lighting New York City. At the time that Edison made his announcement, electric arc lights had been installed in several areas, including the Avenue de l'Opéra in Paris and John Wanamaker's department store in Philadelphia. These lights burned in open globes, emitted a blinding glare and noxious odors, and were wired to the dynamo in series so that they could not be individually operated. Edison was convinced that further work with arc lights would not produce a practical means of household lighting. Instead, he proposed to create an entirely different electric lighting system, one that would be modeled closely on the gas lighting systems that then illuminated many American cities.

Edison's plan seemed visionary. The gas lighting systems then in existence permitted a central gashouse to supply energy via gas mains and smaller branch pipes to thousands of individual jets that could be individually turned on or off. To develop a similar electrical lighting system, Edison not only had to produce a workable light bulb, but had to deal with much more perplexing problems involving electrical resistance, distribution of power, and pressure fluctuation in electrical conductors.

Confident that he could overcome these problems, Edison began work on the project. By choosing to create an entire lighting system rather than a single device, he gained a perspective that eventually allowed him to resolve the difficulties that had stymied other inventors and scientists. He was forced to consider the problems of power distribution and consumption that his predecessors had basically ignored. They had wired their devices to the power source in a series and had constructed low-resistance lights that consumed large quantities of current. Edison realized that such apparatuses were impractical for the lighting network he envisioned, and he decided to investigate other possibilities. He turned his attention to parallel wiring, which would permit each unit to operate independently of the others in a circuit, and he began work on a high-resistance incandescent light bulb that would use little current.

To finance his search for a practical means of electric lighting, Edison's friend and adviser Grosvenor Lowrey persuaded some of the wealthiest people in the United States to invest in the project. In the autumn of 1878 the Edison Electric Light Company was formed to “own, manufacture, operate and license the use of various apparatus used in producing light, heat and power by electricity.” In return for agreeing to assign to the corporation any invention or improvement he might make in electric lighting during the following five years, Edison received 2,500 shares of company stock. For their part, such important financial figures as William Henry Vanderbilt, Western Union president Norvin Green, and J. P. Morgan partner Eggisto Fabbri agreed to pay $50,000 for Edison Electric's remaining 500 shares of stock.

To create a high-resistance incandescent light bulb, Edison first had to find a material that could sustain high temperatures without fusing, melting or burning out. Although he had a substantial knowledge of the uses of carbon from his work with the phonograph, he was unsuccessful in his initial experiments using strips of carbonized paper for the “burner” or “partial conductor” in the glass globe. Similarly fruitless were his efforts, also in the autumn of 1878, to make a burner out of platinum wire. However, these attempts made Edison aware of the need to produce a greater vacuum in his glass container and to calculate the exact resistance of potential burner materials.

Although Edison originally boasted that his lighting system would be completed within six weeks, the project proved to be much more complicated than he had expected. By the end of the winter of 1878-1879, he and his associates at Menlo Park had experimented with a wide variety of materials in their search for a suitable burner. With the new Sprengel pump, they had raised the vacuum in their glass globes to within one or two millimeters of a total vacuum, and in addition they completed extensive mathematical calculations for electrical conductors, lamp resistance, and dynamo capacities. Their efforts yielded a considerable amount of valuable data, but even more work remained ahead.

Throughout the spring and summer of 1879, Edison's team concentrated on three major problems: (1) the development of a dynamo that could power their new lighting system, which would require a constant-voltage current in a multiple circuit; (2) the production of a higher vacuum in the glass globe of their incandescent light bulb; and (3) the search for a perfect incandescent material. By the autumn of 1879 they had completed work on a dynamo that converted steam power into electrical energy with 90 percent efficiency and they succeeded in excluding all but a one-millionth part of an atmosphere from their light globes. However, they were still struggling to find the right incandescent material.

After experimenting with more than 1,500 materials for the burner in his light bulb, by the summer of 1879 Edison had resumed his work with carbon. His earlier work with carbon had been unsuccessful because carbon in its natural state is porous and tends to absorb gases. However, during his year of experimentation Edison had learned that it was possible to expel occluded gases by sending a current through the burner material and heating it at the same time that air was being pumped out of the glass globe of the light bulb. This procedure gave the burner substance a greater resistance to high temperature, and permitted Edison to perfect the light bulb with a carbon illuminant, the precursor of today's modern light bulb.

For months Edison and his associates experimented with threadlike carbon filaments. By October 1879, feeling that success was near, they worked around the clock. After hundreds of tests, their labors were rewarded on October 21, 1879. Using a filament of ordinary cotton thread that had been packed with powdered carbon in an earthenware crucible and then heated to a high temperature, Edison began the ninth of a series of experiments. At 1:30 A.M. he attached the filament to a power source. Thirteen and a half hours later, at 3:00 P.M. the following afternoon, the still -burning light demonstrated the feasibility of electric lighting.

On December 21, 1879, the New York Herald publicized Edison's successful experiment of October 21. The announcement was greeted with amazement, and the Wizard of Menlo Park (as Edison was nicknamed) was praised both in the United States and abroad.