Edison bamboo carbon filament, incandescent lamp, 1881-82. After many experiments, first with carbon filaments 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: it lasted 13.5 hours. Edison continued to improve this design and by November 4, 1879, filed for U.S. patent 223,898 (granted on January 27, 1880) for an electric lamp using "a carbon filament or strip coiled and connected to platina contact wires". This was the first commercially practical incandescent light. This image has been color enhanced.