Sylvania F15T12 with Halophosphate Phopshor
Until the 1930s GE controlled almost the entire global lamp business thanks to its powerful patents, and a licensing scheme that allowed competitors access to its technology but prevented them from growing. Sylvania was one of the largest licensees but was not able to grow beyond 5-6% of GE's sales. The company saw fluorescent as an opportunity to break away from GE's control and it invested enormous efforts in developing its own technology.

Sylvania first studied fluorescence in 1931, and developed a method that is still used for coating glass with phosphors. However its hot cathode design was inadequate, and due to short life the company suspended work in 1934. Activity resumed when learning of the GE and Westinghouse lamps, and the company then redoubled its efforts to not only catch up but take a lead. Whereas GE and W launched their tubes in April 1938, Sylvania impressively followed that autumn.

A vicous lawsuit followed in which GE and Sylvania sued each other for patent infringements - a victorious Sylvania ultimately winning the right to remain an independent manufacturer. Curiously, GE did not promote fluorescent at first, for fear of losing its incandescent dominance - only a few people even knew that fluorescent lamps were more efficient than incandescent. However Sylvania was quick to capitalise on its opportunity. It was first to offer a line of both lamps and luminaires, the famous Miralume series, and its complete system guarantee saw it gain market share rapidly. Later its manufacturing techniques even outstripped those of its competitors in speed and efficiency. This lamp is a later model employing a halophosphate coating, and has black Bakelite caps which were used between 1950-1955.
Manufacturer: Sylvania Electric Products Inc.
Lamp Power: 15 Watts
Lamp Current: 0.33 Amps
Lamp Voltage: 48 Volts
Cap Type: G13 medium b-pin Brass
Bulb Type: T-38 T-12 in eighths/inch
Bulb Finish: White (ZnBe)2SiO4:Mn and MgWO4
Electrodes: Coiled-Coil + Anode Plates (Ba,Sr,Ca)CO3 emitter
Discharge Length: 381 mm 15 inches
Atmosphere: Hg | Ar
Luminous Flux: 650 lm (@ 100h)
Luminous Efficacy: 43.3 lm/W (@ 100h)
Colour Temperature & CRI: CCT: 3500K CRI: Ra 62
Chromaticity Co-ordinates: CCx: 0.405 CCy: 0.391
Rated Lifetime: 2500 hours
Warm-up & Re-strike Time: 2 minutes Instant
Burning Position: Universal
Nominal Length: 457 mm 18 inches
Lighted Length: 419 mm 16.5 inches
Factory: Danvers, MA U.S.A.
Date of Manufacture: April 1950 Date Code: _... / .
Original Value:
 
References: 1) Fluorescent Lamps, C.L.Amick, publ. McGraw-Hill 1942, pp.16,18
2) Fluorescent and Other Gaseous Discharge Lamps, W.E.Forsythe & E.Q.Adams, publ. Murray Hill 1948, pp.95, 99
3) The Electric Lamp Industry, A.A.Bright Jr., publ. Macmillan Company 1949, pp.241, 260, 391, 399-425
4) Photometric measurement of lamp