Incandescent light bulb

• 1. Introduction

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  The incandescent light bulb is an electric light that produces illumination by Joule heating a filament until it glows. For well over a century, that simple idea - sending current through a wire until it shines - lit homes, streets, theatres, and ships across the world. Yet fewer than five percent of the energy an incandescent bulb consumes ever becomes visible light. The rest escapes as heat. How did a device so magnificently inefficient come to dominate the planet's lighting for so long? And who actually deserves the credit for inventing it? The answers involve a transatlantic race, a cartel that secretly throttled bulb lifetimes, a machine that made a thousand bulbs a minute, and a bulb in a California fire station that has been burning, almost without pause, since 1901.

• 2. Pioneers and Patents

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  In 1802, Humphry Davy passed current through a thin strip of platinum using what he described as "a battery of immense size" - a bank of 2,000 cells housed in the basement of the Royal Institution of Great Britain. The light it produced was not bright enough nor long-lasting enough to be practical, but it set off a race among experimenters that would last the next 75 years. Davy also demonstrated the electric arc by passing high current between two pieces of charcoal, and researchers spent the following 40 years trying to turn the carbon arc lamp into something usable at home. Arc lamps burned up their carbon rods rapidly, expelled dangerous carbon monoxide, and tended to produce outputs in the tens of kilowatts - only practical for lighting large areas.

  In 1835, James Bowman Lindsay demonstrated a constant electric light at a public meeting in Dundee, Scotland, claiming he could "read a book at a distance of one and a half feet". He did not develop the idea further. By 1838, Belgian lithographer Marcellin Jobard had invented a bulb using a carbon filament in a vacuum. In 1840, British scientist Warren De la Rue enclosed a coiled platinum filament in a vacuum tube and passed current through it. In 1841, Frederick de Moleyns of England received the first patent for an incandescent lamp. In 1845, American John W. Starr patented a bulb with carbon filaments, though it was never produced commercially. The list of forgotten inventors goes on.

  Historians Robert Friedel and Paul Israel, who surveyed all these predecessors, concluded that Thomas Edison's version was the first practical implementation - not because of a single breakthrough, but because of four combined factors: an effective incandescent material, a vacuum higher than rivals had achieved, a high resistance that made power distribution from a centralized source economically viable, and the development of all the surrounding components needed for a large-scale lighting system. Historian Thomas Hughes put it plainly: the lamp was a small component in Edison's system, no more critical than the Edison Jumbo generator or the parallel-distribution network. Other inventors with comparable ingenuity were forgotten because they never presided over the introduction of a complete system.

• 3. Swan Lights London

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  Joseph Swan, born in 1828 and trained as a physicist and chemist, began experimenting with carbonized paper filaments in an evacuated glass bulb as early as 1850. By 1860, he had a working device, but poor vacuum technology and an inadequate electricity supply meant the bulb lasted only briefly. The tools simply did not yet exist to make it practical.

  By the mid-1870s, better pumps had arrived, and Swan returned to the work. With help from Charles Stearn, an expert on vacuum pumps, he developed in 1878 a method of processing that avoided the early problem of bulb blackening; this received a British Patent in 1880. On the 18th of December 1878, a lamp using a slender carbon rod was demonstrated at a meeting of the Newcastle Chemical Society, though it worked for only a few minutes. Swan repeated the demonstration on the 17th of January 1879, and on the 3rd of February 1879, showed the lamp to 700 people at the Literary and Philosophical Society of Newcastle upon Tyne. That society's building became the first public building to be lit by electricity.

  Swan continued improving the filament. He devised a method of treating cotton to produce what he called "parchmentised thread" in the early 1880s and obtained British Patent 4933 the same year. His own house, Underhill in Low Fell, Gateshead, became the first home in the world to be lit by a lightbulb. In 1880, Mosley Street in Newcastle upon Tyne became the first street in the world lit by incandescent lamps. In 1881, the Savoy Theatre in the City of Westminster, London, was lit by Swan incandescent lightbulbs - the first theatre and the first public building in the world to be lit entirely by electricity. Swan's bulb was not just a demonstration piece: it was installed and in daily use in London in 1881, predating Edison's commercial rollout in Britain.

• 4. Edison's System

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  Thomas Edison began serious research into a practical incandescent lamp in 1878. He filed his first patent application for "Improvement in Electric Lights" on the 14th of October 1878. After many experiments with carbon and then with platinum and other metals, he returned to carbon. The first successful test ran on the 22nd of October 1879, and lasted 13.5 hours. By the 4th of November 1879, he had filed a US patent for an electric lamp using "a carbon filament or strip coiled and connected... to platina contact wires." The patent described several ways of creating the carbon filament, including using "cotton and linen thread, wood splints, papers coiled in various ways". Edison and his team later found that a carbonized bamboo filament could last more than 1,200 hours.

  In 1880, the Oregon Railroad and Navigation Company steamer Columbia became the first application for Edison's incandescent electric lamps and the first ship to use a dynamo. Commercial installation of incandescent lamps at the Mercantile Safe Deposit Company in New York City followed in the fall of 1880, about six months after the lamps had been installed on the Columbia. Among the first Edison bulbs in the Nordic countries were those installed at the weaving hall of the Finlayson's textile factory in Tampere, Finland, in March 1882.

  Back in Britain, after years of legal tension, the Edison and Swan companies eventually merged into the Edison and Swan United Electric Company, later known as Ediswan, which was ultimately incorporated into Thorn Lighting Limited. Edison was initially against the combination, but was eventually forced to cooperate. Swan later sold his US patent rights to the Brush Electric Company in June 1882.

  The United States Patent Office issued a ruling on the 8th of October 1883 that Edison's patents were invalid, based on the prior art of William Sawyer. Litigation continued for years. On the 6th of October 1889, a judge finally ruled that Edison's claim for "a filament of carbon of high resistance" was valid. From an estimated 300,000 general lighting service lamps sold in 1885, the market grew to 88.5 million lamps used in 1914, with only 15% still using carbon filaments. By 1945, annual sales had reached 795 million - more than five lamps per person per year in the United States.

• 5. Better Filaments

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  On the 13th of December 1904, Hungarian Sandor Just and Croatian Franjo Hanaman were granted Hungarian patent No. 34541 for a tungsten filament lamp that lasted longer and gave brighter light than carbon. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1904, and became known in many European countries as Tungsram-bulbs. Tungsten has the highest available melting point of any metal, at 3,695 K - but getting that metal into a workable filament form took years of additional engineering.

  In 1906, William D. Coolidge, working for General Electric, developed a method of making ductile tungsten from sintered tungsten, which could be drawn into wire. By 1911, General Electric had begun selling bulbs with ductile tungsten wire. In 1913, Irving Langmuir found that filling a lamp with inert gas - nitrogen at first, and later argon - instead of a vacuum resulted in twice the luminous efficacy and reduced bulb blackening. He patented that device on the 18th of April 1916.

  In 1917, Burnie Lee Benbow was granted a patent for the coiled coil filament, in which a coiled filament is itself wrapped into a further coil. In 1921, Junichi Miura created the first double-coil bulb using a coiled coil tungsten filament while working for Hakunetsusha, a predecessor of Toshiba. Machinery to mass-produce coiled coil filaments did not yet exist. Hakunetsusha developed the method to mass-produce them by 1936. The advantage of the coiled coil was that gas in the bulb flows only around the outside of the whole coil form, rather than along the wire surface, reducing both evaporation of the filament material and heat loss.

  In 1930, Hungarian Imre Brody filled lamps with krypton gas rather than argon and designed a process to extract krypton from air. Production of krypton-filled lamps based on his invention started at Ajka, Hungary, in 1937, in a factory co-designed by Polanyi and Hungarian-born physicist Egon Orowan. By 1964, improvements in efficiency and production had reduced the cost of providing a given quantity of light by a factor of thirty compared with the cost at the time of Edison's system.

• 6. The Phoebus Cartel

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  Between 1924 and the outbreak of the Second World War, the Phoebus cartel - an agreement among major bulb manufacturers outside North America - attempted to fix prices and sales quotas. Part of what the cartel secretly agreed to was limiting the rated life of incandescent bulbs to 1,000 hours. Early bulbs had been designed for up to 2,500 hours. When the cartel's life-limiting arrangement was exposed in 1953, General Electric and other leading American manufacturers were banned from continuing the practice.

  The physics behind bulb lifetime made the cartel's scheme straightforward to implement. A five percent reduction in operating voltage will double the life of a bulb but reduce its light output by only about 16%. Long-life general service lamps simply trade efficiency for longevity by running the filament at a slightly lower temperature. The 1924 cartel agreement exploited this trade-off in reverse, mandating shorter lives to drive replacement sales.

  The most extreme counter-example to that approach is the "Centennial Light", accepted by the Guinness Book of World Records as having been burning almost continuously at a fire station in Livermore, California, since 1901. The trade-off involved is equally extreme: the bulb emits only the equivalent light of a four-watt bulb. A 40-watt bulb in Texas has been illuminated since the 21st of September 1908 and once resided in an opera house before being moved to a local museum in 1977.

• 7. Making a Thousand a Minute

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  Around 150 bulbs per hour were produced by hand blowing at Corning Glass Works in the 1880s - a team of three workers (two gatherers and a master gaffer) blowing bulbs into wooden or cast-iron molds. Until 1910, that was largely how bulbs were made. That year, Libbey's Westlake machine went into production and changed the arithmetic entirely.

  Corning Glass Works developed competing automated machines, the first of which to enter production was the E-Machine. Corning then installed the Ribbon Machine in 1926 at its Wellsboro, Pennsylvania, factory. The Ribbon Machine works by passing a continuous ribbon of glass along a conveyor belt, heating it in a furnace, and then blowing it through precisely aligned air nozzles through holes in the conveyor belt into molds. The machine's inventor, William Woods, and his colleague at Corning, David E. Gray, had built something that by 1939 was producing 1,000 bulbs per minute. A typical Ribbon Machine can produce between 50,000 and 120,000 bulbs per hour, depending on the bulb size. By the 1970s, 15 ribbon machines installed in factories around the world produced the entire global supply of incandescent bulbs. The 2016 closing of Osram-Sylvania's Wellsboro, Pennsylvania plant meant that one of the last remaining ribbon machines in the United States was shut down.

• 8. Decline and Legacy

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  The luminous efficacy of a typical incandescent bulb is 16 lumens per watt for a 120-volt version, compared with 60 lumens per watt for a compact fluorescent bulb or 100 lumens per watt for typical white LED lamps. The gap is not close, and governments have acted on it. Measures to ban incandescent bulbs by setting minimum efficacy standards higher than incandescent lamps can meet have been implemented in the European Union, the United States, Russia, Brazil, Argentina, Canada, and Australia, among others. The European Commission calculated that its ban saves 40 terawatt-hours of electricity every year and cuts emissions by 15 million tonnes.

  Objections to the bans include the higher upfront cost of alternatives, concerns about the color quality of fluorescent lamps, and resistance to government mandates. A 2017 review in the World Journal of Biological Psychiatry reported that blue-rich white LED lighting can suppress melatonin and disrupt sleep and circadian rhythms, with potential implications for mental illness.

  Efforts to rescue the incandescent were not ignored. In 2007, General Electric announced a high efficiency incandescent lamp project that they claimed could ultimately be as much as four times more efficient than current incandescents. The program was terminated in 2008 due to slow progress. Philips introduced hybrid incandescent bulbs, including the Halogena Energy Saver line, which can produce about 23 lumens per watt - roughly 30 percent more efficient than traditional incandescents - by using a reflective capsule to redirect otherwise wasted infrared radiation back onto the filament. That concept was first commercialized by Duro-Test in 1980, with a product that produced 29.8 lumens per watt. Laboratory proof-of-concept experiments using more advanced reflector designs have reached as much as 45 lumens per watt, approaching the efficacy of compact fluorescent bulbs - though still below LED. The halogen lamp, itself a distinct type of incandescent, remains in production for applications requiring intense concentrated light in a small space, including fiber-optic lamps for optical microscopy.