Edison's Incandescent Lamp

Edison's First Lightbulb as used in Menlo Park demonstration. Source www.classstudio.com/scaltagi/img/internship/sightseeing_day2/edison_bulb.jpg

Inventor Thomas Edison of Menlo Park, New Jersey first patented his carbon-filament lamp on November 1st, 1879. His laboratory first produced promising results for this electrical lamp on October 21st, 1879; a glowing carbonized thread which lasted for more than fourteen (14) hours. Publically demonstrating this invention at Menlo Park on December 31st, 1879, Edison is known to many as the “inventor of the electric light bulb”. However, he is not the inventor of the light bulb, but rather the inventor of the first effective and commercially viable one.

History and Early Research

Early light bulb experimentation dates back as far as 1802, with several other inventors working on the task prior to, during, and after Edison’s own work.

The Arc Lamp

British inventors first demonstrated the possibility of electric light with the arc lamp; a lamp which produced light via an electric arc. Created by Humphrey Davy in 1802, the first instance incandescent light was demonstrated by passing a current through a thin strip of platinum; a metal chosen because of its high melting point. Although it was not very bright or effective as a long-term lighting solution, it created the precedent for the years of scientist’s efforts which followed it.

Early Experiments

In the years following Davy’s invention, many inventors experimented with various materials and constructions for the lamps wires, filaments, and bulb enclosures. In addition to a short lifespan, these early bulbs were expensive and energy ineffective. While, many of these experiments were demonstrated to the public, and several were patented prior to Edison, none were successful at achieving commercial production.

The first instance of an incandescent light bulb, although not well-documented, was in 1835; James Bowman Lindsay publicly demonstrated the first constant electric light in Dundee, Scotland. His device allowed him to read at a distance of one and half feet from the light source. While his incandescent light bulb showed promising results, having satisfied his own requirements for the light he did not improve the bulb further, instead focusing on developing wireless telegraphy.

In 1840, British scientists Warren de la Rue passed an electric current through an enclosed coiled platinum filament in a vacuum tube. The choice of platinum was based on its high melting point which allowed for high temperature operations, while the vacuum tube allowed for less reactivity with the platinum, improving the filament lifespan. Although the bulb’s design demonstrated an effective construction, the platinum filament’s high cost made it impractical for commercial production. In 1841, Frederick de Moleyns was given the first patent for an incandescent bulb, which similarly utilized platinum within a vacuum bulb.

A patent was later granted to American inventor, John W. Starr, for his design for an incandescent light bulb which used carbon filaments. Following his acquisition of the patent, however, he died and his invention never made it to commercial production. Russian inventor Alexander Lodygin similarly invented an incandescent light bulb which utilized carbon rods in a vacuum tube in 1872; he gained a Russian patent for it in 1874. Situated with a glass enclosure, two carbon rods were sealed in with nitrogen and arranged such that in the event that one failed, the electrical current would be passed on to the other. Lodygin later moved to the United States and applied and acquired patents for various incandescent lamp designs which included filaments of chromium, iridium, tungsten, and many other metals.

In 1893, Heinrich Göbel claimed to have invented the first incandescent light bulb in 1854. His design supposedly consisted of thin, high resistance carbonized bamboo filaments, platinum lead-in wires, a glass enclosure, and a high vacuum. His claims, however, were never confirmed and, in fact, discredited in 2007.

On July 24th, 1874 Henry Woodward and Mathew Evans obtained a Canadian patent for an incandescent lamp which consisted of carbon rods mounted in a nitrogen-filled glass bulb. While an effective design, they pair was unsuccessful and commercializing their light bulb and sold the patent rights to Thomas Edison in 1879.

Commercialization

British physicist and chemist, Joseph Swan and American inventor Thomas Edison demonstrated the first instances of commercial production of incandescent lamps. Although Swan began experimenting with incandescent light bulbs earlier, it was Edison’s design which was ultimately adopted.

Swan’s Light Bulb

In 1850, Swan began working with carbonized paper filaments enclosed in evacuated glass bulbs. By 1860 he demonstrated a good working device, but he lacked a vacuum effective enough and an adequate supply of electricity, which resulted in a short lifespan for the bulb and an ineffective light source.

By the mid-1870s, better pumps were created which allowed for modifications to his original design. In 1878, with the help of vacuum pump expert, Charles Stern, Swan developed a bulb production process which avoided the bulb blackening of early designs, obtaining a British patent in 1880.

Swan first demonstrated a new bulb design which used the carbon rods from arc lamps, rather than a thin filament. Because of this design change, the lower resistance filaments required larger conductors in order to supply the necessary current. While impractical for commercial production and having a short lifespan, the bulb design demonstrated the possibilities of incandescent lighting, high vacuum, carbon conductors, and platinum wiring.

The inefficiency of the carbon filament led Swan to experiment with the production of a better one; he began treating cotton in order to produce a “parchmentised thread”, gaining a British patent in 1880. This new carbon filament allowed Swan to begin installing light bulbs in homes and British landmarks that same year, providing lighting for his own house, and even the Savoy Theater, which became the first theater and the first public building to be lit entirely by electricity.