The emission of light by a substance due to its high temperature. For a substance to emit white light, it is required to be heated to above 700ºC. Examples include electric heaters and stoves, and the white-hot filament of a light bulb of an incandescent lamp. British chemist Humphry Davy (1778–1829) demonstrated in 1802 that a strip of metal heated to a temperature using electricity can emit light. To overcome the oxidization of the metal British chemist and physicist Joseph Wilson Swan (1828–1914) invented an electric lamp using a filament of carbonized paper in 1860 but was unable to produce a sufficient vacuum. American inventor Thomas Alva Edison (1847–1931) produced the first practical incandescent light bulb two decades later.