By Nermeen Nabil Khear 
While they are dying out, you can still find incandescent bulbs. While these were once totally common, they’ve been largely replaced by LEDs and other lighting technology. However, you still see a number of them in special applications or older gear. If you are above a certain age, you might be surprised that youngsters may have never seen a standard incandescent lightbulb. Even so, the new bulbs are compatible with the old ones, so — mechanically, at least — the bulbs don’t look different on the outside.
It has been known for a long time that passing a current through a wire creates a glow. The problem is, the wire — the filament — would burn up quickly. The answer would be a combination of the right filament material and using an evacuated bulb to prevent the filament degrading. But it took over a century to get a commercially successful lightbulb.
We were all taught in school that Thomas Edison invented the light bulb, but the truth is much more complicated. You can go back to 1761 when Ebenezer Kinnersley first caused a wire to glow. Of course, wires would quickly burn up in the air. By the early 19th century, limelight was fairly common in theaters. Limelight — also known as the Drummond light — heated a piece of calcium oxide using a gas torch — not electric, but technically incandescence. Ships at sea and forts in the U.S. Civil War used limelights to illuminate targets and, supposedly, to blind enemy troops at night. Check out the video below to see what a limelight looks like.
Sir Humphry Davy demonstrated a dim, impractical light that used a huge battery and a thin strip of platinum. More practical was Davy’s electric arc lamp, which, after being refined by others, became common in some applications.
Arc lights had issues, though. They hissed and flickered. The carbon rods emitted carbon monoxide and ultraviolet light. They were extremely harsh and bright, and the rods burned up quickly. Everyone knew a better light bulb would be a winner, but no one knew how to create it.
Getting Closer
Starting around 1835, there were many experiments and demonstrations, but none of them really caught on. A Belgian, Marcellin Jobard, was on the right track in 1838 with a lightbulb in a vacuum with a carbon filament, but nothing really came of it. He also came up with what amounts to early emojis, but that took a long time to catch on, too.
Since platinum has a high melting point, it was a popular filament candidate. In the 1840s and 1870s, many inventors used platinum or carbon with varying degrees of success. During that same time period, there were many patents and demonstrations, but none were successfully commercialized. However, a Russian named Alexander Lodygin did patent a working bulb with carbon rods in nitrogen gas.
It isn’t clear if Henry Woodward and Mathew Evans knew of the Russian patent. In 1874, they filed a Canadian patent for a similar bulb. Ultimately, they failed to commercialize it, but they sold their patent to Thomas Edison.
Edison
Edison got serious about electric lighting in 1878. He experimented with different carbonized materials and platinum but finally settled on carbon fed by platinum wires. Using carbonized threads resulted in a bulb that lasted just over 13 hours. However, he would discover that carbonized bamboo could last 1200 hours. You can see one of the oldest surviving Edison bulbs at the Port Huron Museum and in the video below.
Many people worked on the problem throughout the 1800s. Edison arrived at a practical solution and had the mechanism in place to exploit it. However, others had light bulb patents. Albon Man and William Sawyer had bulbs that didn’t last as long as Edison’s but formed the basis for the United States Electric Lighting Company. That company’s chief engineer was Hiram Maxim, a name familiar to most ham radio operators, but this particular Hiram Maxim was the famous ham radio operator’s father.
The elder Maxim is one of several people who claimed they had actually invented the incandescent light before Edison. The courts eventually decided that some of Edison’s claims were preempted by William Sawyer’s patents, but that Edison still had other valid patent claims.
Modern Types
These early bulbs had little in common with modern bulbs. The inside of the bulb had to have very little oxygen and moisture, or the filament would oxidize or burn out. Initially, mercury vapor pumps and phosphoric anhydride were used, but this added expense to bulbs. Arturo Malignani found that red phosphorus would allow for a drier vacuum with cheaper pumps. Edison was quick to buy the patent.
However, Lodygin and others were on the right track, and using a metal filament and an inert gas to replace the oxygen would be more effective. This prevents the filament from burning and also reduces the evaporation of the filament. (See the video below if you want to see the effect of air on a tungsten filament.) He invented a process for forming thin metal filaments and sold the patent to General Electric in 1902.
The truly modern bulb is the result of a 1904 invention by Sándor Just and Franjo Hanaman. They created a tungsten filament that worked better in an argon or nitrogen atmosphere. The Hungarian company Tungsram sold these, and they could practically pass for a modern clear-glass bulb.
A modern bulb has a glass envelope and a tungsten filament, although they add a few impurities to increase the filament life. The bulb contains a low pressure of a gas like argon, nitrogen, krypton, or xenon. Modern glass bulbs are either clear or coated with kaolin clay from the inside. Some bulbs have pigments to change color or different glass to produce different colors. Bulbs used for heating sometimes have special glass or even fused quartz.
Real World Considerations
Light bulbs are one of those circuit elements we pretend are perfect, but they aren’t. Tungsten filaments have a low resistance when cold, which causes a bulb to draw a lot of current when it first turns on. As the filament gets hot, the resistance goes up, and the current goes down. Oddly enough, carbon filaments have the opposite problem. They draw more power as they get hot, which also makes them sensitive to power surges, since if they get hot, they draw more current, which causes them to draw even more current, which makes them even hotter, and the cycle repeats.
In high-reliability circuits, designers often highly derate a bulb’s specifications to get a dimmer light that lasts longer. A 5% reduction in voltage will roughly double a bulb’s lifetime but also make it about 16% dimmer. Some will also pass a small current through the bulb even when it is off to keep the filament warm. This reduces the current draw and heating associated with turning on a cold filament.
The other big problem with incandescent lights is that they are relatively inefficient since most of the energy produces heat and infrared light. A typical bulb is around 5% efficient in terms of visible light, and the best halogens come in around 10%.
Of course, this inefficiency is why there’s been a move to ban incandescent bulbs in favor of LEDs, fluorescents, and other technologies. LED lights, in contrast, can reach 30-40% efficiency. Still more light than heat, but almost an order of magnitude more efficient than plain-old incandescents.
So Much More
There’s a lot more to learn about light bulbs. In 1885, the U.S. had an estimated 300,000 carbon filament bulbs. By 1914, there were 88.5 million. In 1945, the market was around 795 million. When you deal with that kind of scale there are many innovations both in the technology and the machinery used to build them. Want to see how lightbulbs were made? Check out the video below.
We’ve talked about the early lighting market and one of its pioneers, Lewis Latimer, a few years ago. We’ve looked at the checkered history many times.
Featured image: “Yellow Bulb” by [Daniel Reche]
This articles is written by : Nermeen Nabil Khear Abdelmalak
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