Edison's incandescent lamp: carbonized-thread test, patent application and first public demonstration

Background. In 1878, Edison began working on a system of electrical illumination that he could deploy as a large-scale commercial utility, hoping it could compete with gas and oil-based lighting. He first tried a filament made of cardboard, carbonized with compressed lampblack, but it burnt out too quickly to provide lasting light. The patent he later filed described several ways of creating a carbon filament, including cotton and linen thread, wood splints, and papers coiled in various ways.

Patent Application. Edison filed for U.S. Patent 223,898 on 4 November 1879. The patent described an electric lamp using a carbon filament or strip coiled and connected to platina contact wires. It covered various methods of creating the carbon filament, including using cotton, linen thread, wood splints, and papers. The patent was granted on 27 January 1880.