GIANT COILS ARE FASHIONED AT NELA PARK TO SHOW NEW, OLD FILAMENT DESIGN
CD 1964017 E&MP25.075
MAR 7, 1938
Ordinarily, the intricate twists and turns of the new high-efficiency tungsten filaments used in General Electrics 60-watt lamps are too minute to be seen without aid of a powerful microscope.
Hence the two giant aluminum coils pictured in the accompanying photo. Both of these models -- made up recently by G-Es incandescent lamp department at Nela Park, Cleveland -- show at a glance the difference between new and old filament construction.
The large coil in the young ladys hand represents a small section of the new 60-watt high-efficiency filament which recently increased light output ten percent. The other coil shown represents the simpler, though much longer, type of filament formerly used in the companys 60-watt lamps.
Whereas the wire used in the model filaments is nearly pencil-thick, the hairlike tungsten wire in the twice-coiled high efficiency filaments is less than two thousandths of an inch in diameter. Width of the complicated tungsten coil is approximately that of a common pin.
Although the intricate high-efficiency filament burns at temperatures nearly twice those at which Bessemer steel melts, the tiny heart of the 60-watt lamp remains as is throughout its designed life of one thousand 60-watt lamp remains as is throughout its designed life of one thousand hours.