F15T8 with Zinc Beryllium Silicate Phopshor

As GE's only 'A-Licensee', Westinghouse enjoyed full rights to all patents and the two 'competitors' co-operated on the development of the first fluorescent lamps. Thus it was natural for both companies to simultaneously announce identical fluorescent lamps on 27th November 1937, with their full commercial launches following on 1st April 1938.

This lamp is representative of the first model. It is made in T8 glass only because that size was available from Lumiline lamps. The 18" length was chosen because when driven at 0.25 amperes, for which the first electrodes were developed, the resulting power of 15W delivered the most efficient lamp whose voltage was low enough to operate with a simple choke ballast from 110-120V mains voltages. The first lamps had instant-start electrodes and single contact Lumiline caps, but this presented difficulties in manufacture. Before the commercial introduction, the design was changed to preheated cathodes with the familiar bi-pin caps, and due to an increase in electrode efficiency, lamp current was raised to 0.30A so as to maintain the power of 15W.

The next lamp was made with T12 glass but same power and length to offer lower surface brightness, and it was noted that it had a lower voltage. While maintaining a choke ballast, that permitted the length to be increased and yielded a third lamp, the more powerful rating of 24" 20W. A lamp for high mains voltages then followed, achieved by doubling the length of the 15W T8 lamp to arrive at the 36" long 30W T8 model. It was these four models that were launched simultaneously as the starting range. All employ a mixture of pale yellow fluorescing zinc beryllium silicate and blue fluorescing magnesium tungstate to achieve white light.
Manufacturer: Westinghouse
Lamp Power: 15 Watts
Lamp Current: 0.300 Amps
Lamp Voltage: 56 Volts
Cap Type: G13 medium bi-pin Steel
Bulb Type: T-26 T-8 in eighths/inch
Bulb Finish: White (ZnBe)2SiO4:Mn and MgWO4
Electrodes: Coiled-Coil + Anode Plates (Ba,Sr,Ca)CO3 emitter
Discharge Length: 394 mm 15.5 inches
Atmosphere: Hg | Ar
Luminous Flux: 585 lm (@ 100h)
Luminous Efficacy: 39.0 lm/W (@ 100h)
Maximum Brightness: 7000 lux 2040 foot-lamberts
Colour Temperature & CRI: CCT: 3500K CRI: Ra 72
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
Factory: Fairmont, VA U.S.A.
Date of Manufacture: circa. 1945
Original Value: US $0.57 (1942-46)
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, p.391
4) Photometric measurement of lamp