Soon after, in 1880, Thomas Edison sealed thin filaments of carbonized threads inside a glass bulb from which all air had been removed by a vacuum, and then passed an electric current through them. The voltage was steadily increased until the incandescent filament reached a stable, bright glow. The electric current kept the filament glowing for 40 hours. Although the melting point of carbon is quite high, 3,598 °C, the material is evaporated at a much lower temperature, and carbon filament lamps had to be operated at a low temperature in order to prolong their life. In took another three decades until the tungsten filament was developed, in 1909.

Edison was faster to register a patent on his lamp than Swan . Edison's invention marked the dawn of electric lighting and the electric age.

Incandescent Theatre Lighting

One of the first lighting systems of incandescent bulbs fed by an electric power source was installed in the Savoy Theatre in London, which opened in October 1881. The electric power was generated by a giant steam engine of 120 horsepower, supplied by the German company Siemens and placed outside the theatre, and the entire theatre was illuminated with 1200 Swan incandescent bulbs. There were however serious technical problems, caused mainly by interruptions in the electricity supply, the result being that the lighting rose and fell during the performance with no relationship whatsoever to events on stage. Despite these teething problems the new lighting system was enthusiastically received by public and press alike.

The first performances at the Savoy were operettas by Gilbert and Sullivan, who even dedicated a song to the wonders of stage lighting. On December 1881, the 'Times' wrote: "An interesting experiment was made at a performance of 'Polience' yesterday afternoon, when the stage was for the first time lit up by the electric light … The success of the new mode of illumination was complete … the effect was pictorially superior to gas."

Like many innovations, the installation of electric systems in theatres was accompanied by suspicion on the part of the audience which, remembering the mishaps and fires caused by gaslight systems, feared that electrical systems were not safe enough. D'Oyly Carte, manager of the Savoy Theatre, came on stage and enveloped an electric lamp with a piece of highly inflammable muslin. He then broke the glass, demonstrating how the vacuum killed the flame immediately without even singeing the muslin.

The manager of the Olympic Theatre was less certain of the fidelity of this new invention, and announced to the audience that the theatre did not completely trust either electricity or gas, and undertook that every evening, in every corner of the theatre, there would also be oil lamps!

Nevertheless by the turn of the century nearly all theatres in Europe and the US had replaced their now obsolete gaslight with new electric systems, and the use of gas in the theatre was forbidden by the authorities.

Effect of Electric Light on the Theatre

The light generated by the filament lamp was even stronger than that of gaslight, and its introduction into the theatre had a major influence on both scenery and makeup, since every tiniest detail of scenery or makeup was now glaringly visible.

In many theatres the existing gaslighting apparatus was refurbished. In this theatre, old borderlights, winglights and footlights were fitted with electric lamps instead of the obsolete gas burners and the rotating color cylinders, which had been used in the gaslight period, were retained. Many theatres maintained the old configuration of the gaslight systems well into the 20th century.

The transition from gaslight to electric light was significant not only because of the intensity and the quality of the light of the incandescent bulb, but also due to the inherent potential electricity has for more precise control of light intensities. On December 29, 1881, the 'Times' wrote: "The ordinary electric apparatus has the great drawback for stage representation that the flame can not be lowered or increased at will, there being no medium between full light and total darkness". But the writer continues to state that this difficulty has been successfully overcome by "interposing into the circuit through which the lamp receives the current what in technical language is called a 'resistance'…" - a fair description of the first electrical dimmers in the theatre. This method of dimming by resistance was used for years, side by side with other methods, all of which were eventually replaced by the electronic dimmer.