History of Edison Bulbs: What material was the filament of Edison's light bulb?

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History of Edison Bulbs: What material was the filament of Edison's light bulb?

Edison bulbs, aka filament bulbs, are those antique-looking light bulbs that you can look at directly without hurting your eyes. They are therefore often used bare, and they typically add a rustic or vintage accent to a room. Let's find out how they are different from regular, modern incandescent bulbs, and see if we find any surprising facts about the Wizard of Menlo Park himself, Thomas Edison, and his role in the invention of electric light bulbs. 

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The filament of Edison's light bulb

When Edison and his researchers at Menlo Park became interested in the artificial lighting, they focused on improving the filament -- first testing carbon, then platinum (platinum was good - but too expensive), before finally returning to a carbon filament.

By October 1879, Edison’s team had produced a light bulb with a carbonized filament of uncoated cotton thread that could last for 14.5 hours.

They continued to experiment with the filament until settling on one made from bamboo that gave Edison’s lamps a lifetime of up to 1,200 hours -- this filament became the standard for the Edison bulb for the next 10 years. Edison also made other improvements to the light bulb, including creating a better vacuum pump to fully remove the air from the bulb and developing the Edison screw (what is now the standard socket fittings for light bulbs).  He got the idea of the Edison screw (the part of the bulb that literally screws into the power source) while looking at a gas can.  The tops of gas cans have a screw-like top so when lid is screwed in the gas cannot spill from the can.

Thomas Alva Edison in his laboratory

Though we all accept that he was the 'inventor' of the light bulb, by the time Edison began his experiments with light bulbs, the general structure and technology for incandescent bulbs was already in place: a glass bulb evacuated of oxygen housing a filament of carbonized material that would glow but not burn when electrified. The crucial developments that laid the groundwork for Edison's success were achieved by more than a dozen scientists throughout the 19th century, most prominently by a British scientist named Joseph Swan, whose earlier published research was similar enough to Edison's prototype that he eventually won a court victory in Britain granting him partnership in Edison's UK business, very much against Edison's will.

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To Edison's credit, while he was a canny self-promoter, he also coined the phrase, "genius is 1% inspiration and 99% perspiration," which is an accurate and fair description of how he succeeded. He may have relied in part on the inspiration of his peers and predecessors — after all, many inventors and developers do — but he set himself apart with tireless research and experimentation. Joseph Swan's bulb had all the necessary components to function, but it didn't last very long. Edison determined that the key to creating a commercially viable bulb was finding the right material for the filament, one that would last for a long time before burning out. He contacted biologists for help in his search, and by his own count, he ultimately tested the carbonized filaments of more than 6,000 plant species in his search for a long-burning material. He finally settled on bamboo, and in 1880 he created a 16-watt bulb that could burn for over 1200 hours, finally a technology superior to the gas lamp and marketable to the general public.

Edison was embroiled in litigation and other vagaries of competition for the next couple of decades, but the incandescent bulb was already a massive success, especially as other scientists continued to improve on the technology, developing tungsten filaments that burned even longer than the bamboo and that didn't blacken the inside of the bulb.

standard base incandescent edison bulb

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