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A Short History of the Incandescent Bulb
December 15, 2019
The story of the light bulb is one of luck, dutiful lab work, finances, and patent battles. While Thomas Edison is closely associated with the light bulb, he didn’t exactly invent it; he was actually in a close race with other engineers to make the extant idea of an incandescent filament bulb commercially feasible. And his breakthrough wasn’t the eureka moment that his invention has come to represent; it was a grinding process of experimentation and elimination made possible in part by his company’s considerable revenue and superior technology. The result was something simple and lasting. Quite literally—one light bulb made during Edison’s lifetime is still aglow. But it’s an old technology, and inefficient on a basic, physical level compared to newer options. Let’s shed some light on the matter.
Looking At The Numbers
Incandescent bulbs have two important features: the filament and the vacuum or inert gas that surrounds it. The filaments are often curly because there’s a thin layer of non-moving gas around them called the Langmuir sheath—more filament surface area means a bigger sheath, which means the heat of the filament dissipates more slowly, making it more efficient. A bulb is an electrical circuit with one piece—the filament—that offers high resistance to the electricity trying to flow through it. That excites the atoms in the filament, so it gets hot. At 850 Kelvin it starts to emit visible light(pdf). Tungsten is typically used for the filament in an incandescent bulb because it has a high melting point and a low rate of evaporation, so it can stay very hot (over 2500 K) without melting or vaporizing. The vacuum or inert gas is necessary to prevent the filament from reacting with oxygen and exploding. That was a critical part of Edison’s success—he was better able to create a vacuum in his bulb than his closest competitor, who had been working on the concept for much longer.
As with computers, the story of the light bulb begins with an expensive, room-sized device with no consumer application. What was arguably the first light bulb contained a carbon-arc light designed by Humphry Davy, a British chemist most famous for his miner’s safety lamp, isolating elements such as sodium and potassium, and for mentoring Michael Faraday. Experimenting with a battery, he saw light jump across a gap in a circuit, and had a flash of inspiration. But his demonstration of electric lighting for the Royal Institution of London in 1809 required a room filled by a 2,000-cell battery. Arc lights are essentially bolts of lightning, and as such, require a lot of power and generate a lot of light. It took about 70 years for Davy’s invention to acquire a sufficiently practical power source, when electrical prodigy Charles F. Brush used a dynamo, a type of mechanical generator, to power streetlights in Cleveland, Ohio in 1879. Davy’s basic idea is still in use when an intense beam of light is needed, as in a movie theater or a lighthouse.
That same year, Thomas Edison got his first filament light bulb working, and soon produced the first commercially successful version. The idea though, dated back to 1840 when Warren de La Rue, another British chemist, successfully chose a metal with a high melting point for the filament. Unfortunately, it was platinum, which suffered from the same price-point problem it does today.
Yet another British chemist, Joseph Swan, nearly beat Edison to the first viable filament light bulb . But Swan had two problems. First, existing vacuum-pump technology limited his bulbs’ potential for decades. Second, Swan’s filament was carbonized paper; in the absence of a sufficient vacuum, it reacted with oxygen and filled the bulb with soot. Edison, meanwhile, had cutting-edge equipment and armies of lab assistants to throw at the problem, thanks to prior inventions. He used a modified Sprengel pump, a new addition to his lab, to reduce the atmospheres in the bulb from 1/100,000 to 1/1,000,000. After cycling through thousands of materials, he landed on carbonized bamboo for the filament, which was stronger and had higher electrical resistance than carbonized paper. Swan got his bulbs to run for 40 hours; Edison’s bamboo filaments lasted 1,500, comparable to modern tungsten bulbs. But Swan got some good parting gifts. Patenting his similar invention in Britain meant that Edison had to partner with and buy Swan out there, and Swan’s bulbs were the first to light a public building.
That warm glow of an incandescent light? It’s too warm; 90% of the electricity that powers it is released as heat. LEDs have the opposite ratio, producing light through electroluminescence, which, like the arc light, was discovered in a happy accident. Experimenting with crystal detectors at the dawn of the radio age in 1907, H.J. Mounds applied a direct current to silicon carbide, which lit up. Later research demonstrated why: Crystal growth in the material diode. At the heart of an LED is a p-n junction (pdf) between semiconductor materials, one that has been “doped” to have more electrons (n-type for negatively charged) and one doped to have fewer (p-type for positively charged). Electrons from the n-type fill the “holes” in the p-type. When that happens, the electrons go from a higher orbit (high energy) to a lower orbit (low energy) around the atoms. The energy loss is expressed as a photon—light. The color depends on the wavelength of the photons, which depends on the chemistry of the semiconductors. General Electric scientist Nick Holonyak, Jr. produced the first practical LED, in red, in 1962, which is why so many calculators and watches had a crimson hue. It took another decade to get a yellow one. Shortly thereafter green followed. To replace the incandescent bulb, LEDs needed to be white, requiring a mix of red, green and blue. That didn’t happen until the 1990s, because of the difficulty of growing and doping the gallium nitride crystals required; the blue LED was such an achievement that it won three Japanese physicists the Nobel Prize in 2014. LED bulbs still aren’t quite as good in rendering color as incandescent lights, but they’re pretty close. And although they are more expensive than incandescent bulbs, they are far more environmentally friendly, and their efficiency often pays for itself in a matter of months. Plus, you rarely have to go to the trouble of changing them.
How did the “Edison bulb”—an exposed bulb with a carbon filament releasing a gentle orange glow—become synonymous with 21st-century restaurant design? The design firm Bentel & Bentel wanted to express the concept of “craft” for a restaurant of the same name by star chef Tom Colicchio. They found the style in the catalog of a lighting distributor, who had discovered them being made on vintage equipment in what was then Czechoslovakia. A drive past a construction site sealed the aesthetic.
Figure 1: 1879: Thomas Edison Crowns 14 Months Of Testing With An Incandescent Electric Light Bulb That Lasts 13½ Hours.
December 15, 2019
The story of the light bulb is one of luck, dutiful lab work, finances, and patent battles. While Thomas Edison is closely associated with the light bulb, he didn’t exactly invent it; he was actually in a close race with other engineers to make the extant idea of an incandescent filament bulb commercially feasible. And his breakthrough wasn’t the eureka moment that his invention has come to represent; it was a grinding process of experimentation and elimination made possible in part by his company’s considerable revenue and superior technology. The result was something simple and lasting. Quite literally—one light bulb made during Edison’s lifetime is still aglow. But it’s an old technology, and inefficient on a basic, physical level compared to newer options. Let’s shed some light on the matter.
Looking At The Numbers
- £9,375 ($12,315): Price for a carbon-rod-filament lamp made in 1877 by Joseph Swan at a 2018 auction
- $40,000: Cost to produce Edison’s first demonstration bulb over 14 months and 1,200 experiments ($1.1 million in 2019 dollars)
- $260: Cost of a single light-emitting diode (LED) in 1962 ($2,230 in 2019 dollars)
- 117: Years the Centennial Bulb has been in operation at a fire station in Livermore, California (over one million hours)
- 40: Average number of light bulbs in the American household
- 15%: Share of global energy consumption that goes to lighting
- 1,000: Photons scattered from a single electron by a laser at the University of Nebraska, creating a light one billion times brighter than the surface of the sun (electrons usually only scatter a single photon at a time)
Incandescent bulbs have two important features: the filament and the vacuum or inert gas that surrounds it. The filaments are often curly because there’s a thin layer of non-moving gas around them called the Langmuir sheath—more filament surface area means a bigger sheath, which means the heat of the filament dissipates more slowly, making it more efficient. A bulb is an electrical circuit with one piece—the filament—that offers high resistance to the electricity trying to flow through it. That excites the atoms in the filament, so it gets hot. At 850 Kelvin it starts to emit visible light(pdf). Tungsten is typically used for the filament in an incandescent bulb because it has a high melting point and a low rate of evaporation, so it can stay very hot (over 2500 K) without melting or vaporizing. The vacuum or inert gas is necessary to prevent the filament from reacting with oxygen and exploding. That was a critical part of Edison’s success—he was better able to create a vacuum in his bulb than his closest competitor, who had been working on the concept for much longer.
As with computers, the story of the light bulb begins with an expensive, room-sized device with no consumer application. What was arguably the first light bulb contained a carbon-arc light designed by Humphry Davy, a British chemist most famous for his miner’s safety lamp, isolating elements such as sodium and potassium, and for mentoring Michael Faraday. Experimenting with a battery, he saw light jump across a gap in a circuit, and had a flash of inspiration. But his demonstration of electric lighting for the Royal Institution of London in 1809 required a room filled by a 2,000-cell battery. Arc lights are essentially bolts of lightning, and as such, require a lot of power and generate a lot of light. It took about 70 years for Davy’s invention to acquire a sufficiently practical power source, when electrical prodigy Charles F. Brush used a dynamo, a type of mechanical generator, to power streetlights in Cleveland, Ohio in 1879. Davy’s basic idea is still in use when an intense beam of light is needed, as in a movie theater or a lighthouse.
That same year, Thomas Edison got his first filament light bulb working, and soon produced the first commercially successful version. The idea though, dated back to 1840 when Warren de La Rue, another British chemist, successfully chose a metal with a high melting point for the filament. Unfortunately, it was platinum, which suffered from the same price-point problem it does today.
Yet another British chemist, Joseph Swan, nearly beat Edison to the first viable filament light bulb . But Swan had two problems. First, existing vacuum-pump technology limited his bulbs’ potential for decades. Second, Swan’s filament was carbonized paper; in the absence of a sufficient vacuum, it reacted with oxygen and filled the bulb with soot. Edison, meanwhile, had cutting-edge equipment and armies of lab assistants to throw at the problem, thanks to prior inventions. He used a modified Sprengel pump, a new addition to his lab, to reduce the atmospheres in the bulb from 1/100,000 to 1/1,000,000. After cycling through thousands of materials, he landed on carbonized bamboo for the filament, which was stronger and had higher electrical resistance than carbonized paper. Swan got his bulbs to run for 40 hours; Edison’s bamboo filaments lasted 1,500, comparable to modern tungsten bulbs. But Swan got some good parting gifts. Patenting his similar invention in Britain meant that Edison had to partner with and buy Swan out there, and Swan’s bulbs were the first to light a public building.
That warm glow of an incandescent light? It’s too warm; 90% of the electricity that powers it is released as heat. LEDs have the opposite ratio, producing light through electroluminescence, which, like the arc light, was discovered in a happy accident. Experimenting with crystal detectors at the dawn of the radio age in 1907, H.J. Mounds applied a direct current to silicon carbide, which lit up. Later research demonstrated why: Crystal growth in the material diode. At the heart of an LED is a p-n junction (pdf) between semiconductor materials, one that has been “doped” to have more electrons (n-type for negatively charged) and one doped to have fewer (p-type for positively charged). Electrons from the n-type fill the “holes” in the p-type. When that happens, the electrons go from a higher orbit (high energy) to a lower orbit (low energy) around the atoms. The energy loss is expressed as a photon—light. The color depends on the wavelength of the photons, which depends on the chemistry of the semiconductors. General Electric scientist Nick Holonyak, Jr. produced the first practical LED, in red, in 1962, which is why so many calculators and watches had a crimson hue. It took another decade to get a yellow one. Shortly thereafter green followed. To replace the incandescent bulb, LEDs needed to be white, requiring a mix of red, green and blue. That didn’t happen until the 1990s, because of the difficulty of growing and doping the gallium nitride crystals required; the blue LED was such an achievement that it won three Japanese physicists the Nobel Prize in 2014. LED bulbs still aren’t quite as good in rendering color as incandescent lights, but they’re pretty close. And although they are more expensive than incandescent bulbs, they are far more environmentally friendly, and their efficiency often pays for itself in a matter of months. Plus, you rarely have to go to the trouble of changing them.
How did the “Edison bulb”—an exposed bulb with a carbon filament releasing a gentle orange glow—become synonymous with 21st-century restaurant design? The design firm Bentel & Bentel wanted to express the concept of “craft” for a restaurant of the same name by star chef Tom Colicchio. They found the style in the catalog of a lighting distributor, who had discovered them being made on vintage equipment in what was then Czechoslovakia. A drive past a construction site sealed the aesthetic.
Figure 1: 1879: Thomas Edison Crowns 14 Months Of Testing With An Incandescent Electric Light Bulb That Lasts 13½ Hours.
Source: ieee. org