The filament that started it all: carbonized bamboo
Light from fibrous green shoots.
If you’re like me, you might think you know a bit about how the first light bulb was invented, but I’m guessing that you’re wrong about most of it. Read on to cure your ignorance.
Most school children in the US learn that Thomas Edison invented the light bulb in 1878. This is partly correct. Thomas Edison invented a commercially viable lightbulb in 1878, but people had been using electricity to create light as early as 1802. Those early attempts worked, but they were expensive and impractical.
One of the key issues was the filament. The word filament is Latin for “thread.” Today, the word basically just refers to that thin bit of material visible in clear incandescent light bulbs. We take for granted that incandescent light bulbs can produce light for thousands of hours, but in the 1800s, the search for a material that could conduct electricity and generate light for more than an hour or two was very much in the early research process.
The problem was substantial: the filament needed to efficiently convert electrical energy into visible light without being vaporized or melted. One of Edison’s first innovations was to produce glass bulbs capable of being evacuated, IE having the air inside pumped out to form a vacuum. This was critical because the oxygen in air reacts with most filament materials that are electrified, causing them to burn out like the wick of a candle.
With a vacuum-sealed bulb, Edison’s first filament made of platinum was able to generate light for hours at a stretch. But platinum was expensive, and people were unlikely to be satisfied with a light bulb that couldn’t even operate for a single night. The competing technology at the time - gas and whale oil lanterns - were cheaper and lasted longer.
Through the process of iterative testing, Edison’s laboratory employees discovered a superior material: carbonized bamboo. These early filaments were capable of emitting light in a vacuum-sealed glass bulb for up to 1,200 hours.
The actual process of making these filaments involved taking a narrow and flexible strand of bamboo, shaping it into the desired shape, heating it in an oven to carbonize it, and then inserting it (delicately!) into the bulb. The air in the bulb would then be removed and electricity could be applied to the filament. This video does a good job of visualizing what this looks like.