Edison's patent application for paper carbon filament light bulb filed on December 8, 1878. Edison began research into developing a practical incandescent lamp in 1878. He filed his first patent application for "Improvement In Electric Lights" in October 1878. After many experiments, first with carbon in the early 1880s and then with platinum and other metals, in the end Edison returned to a carbon filament. The first successful test was on October 22, 1879, and lasted 13.5 hours. Edison continued to improve this design and by November 4, 1879, filed for a US patent for an electric lamp using "a carbon filament or strip coiled and connected to platina contact wires." An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated to a high temperature, by passing an electric current through it, until it glows with visible light (incandescence). The hot filament is protected from oxidation with a glass or quartz bulb that is filled with inert gas or evacuated.