Edison wrote all the 1600 kinds of heat-resistant materials he could think of on paper and tried them one by one. One night, Edison, who had worked all day, was thinking and absently rubbing a piece of compressed bituminous coal in his hand. Unconsciously, bituminous coal has been rubbed into thin threads. He suddenly wanted to see if the thin thread in his hand would help the experiment.

Edison cut it into small pieces, smoked it in the furnace for about 1 hour, then put it in a glass bubble to remove some air, and then turned on the current. The fragile silk thread immediately released dazzling light. Careful Edison found that filaments became extremely hard after carbonization. Although the carbon filament lamp was only on for a short time, it brought the hope of success to the research of electric lamp.

1879101October 2 1 day, Edison, with the help of a glass expert, pumped the light bulb into a near vacuum state with a new air pump and then sealed it. When the current is switched on, the filament emits golden light in a vacuum state for 45 hours continuously. This day is also permanently recorded in history.