Fluorescent Blue with Calcium Tungstate Phosphor

When GE launched the first commercial fluorescent lamps in 1938, the company did not expect them to become popular for general lighting. The early white colours were about 2-3 times as efficient as incandescent lamps, but it was not known how customers would react to the tubular shape, different light distribution, colour rendering quality, along with the relatively high price, the need for complex electrical control gear and entirely new luminaires.

The fluorescent colours however were considerably more efficient than filtered incandescent lamps. As such it was considered that the primary application of fluorescent lamps would be in architectural and decorative applications, alongside the 'Lumiline' linear incandescent lamps that the company had pioneered in 1934. As such the fluorescent lamp was launched not only in white and daylight, but five additional colours of blue, green, gold, red and pink.

Blue light was produced with calcium tungstate, green with zinc silicate, and pink with cadmium borate. Gold was achieved with a zinc-beryllium-silicate modified to a yellower hue, plus a pigment to remove shorter wavelengths. Similarly, red was attained with cadmium borate plus a red pigment. This blue lamp in fact employs a high-brightness calcium tungstate phosphor, which was used from the outset. Calcium tungstate is unusual in that it does not require any activator - however it was found that trace impurities of lead function as an activator that improves efficacy by producing a longer wavelength shift, albeit with slightly less colour saturation. In parallel, incorporation of a slight excess of CaO beyond the stoichiometric requirement to form CaWO4 leads to another increase in brightness.
Manufacturer: General Electric Co. of U.S.A.
Lamp Power: 15 Watts
Lamp Current: 0.300 Amps
Lamp Voltage: 56 Volts
Cap Type: G13 medium bi-pin Brass
Bulb Type: T-26 T-8 in eighths/inch
Bulb Finish: Blue CaWO4:Pb
Electrodes: Coiled-Coil (Ba,Sr,Ca)CO3 emitter
Discharge Length: 394 mm 15.5 inches
Atmosphere: Hg | Ar
Luminous Flux: 315 lm (@ 100h)
Luminous Efficacy: 21.0 lm/W (@ 100h)
Maximum Brightness: 3855 lux 1125 foot-lamberts
Chromaticity Co-ordinates: CCx: 0.187 CCy: 0.196
Dominant Wavelength & Saturation: 477 nm 63%
Rated Lifetime: 1500 hours
Warm-up & Re-strike Time: 2 minutes Instant
Burning Position: Universal
Nominal Length: 457 mm 18 inches
Factory: Jackson MI / Bucyrus OH U.S.A.
Date of Manufacture: circa. 1941
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.119-120, 186, 191-192
3) Lamps for a Brighter America, P.W.Keating, publ McGraw-Hill 1954, pp.198-201
4) US Patent 2,132,273, Fluorescent Material, W.A. Roberts (General Electric), Filed October 1936
5) Photometric measurement of lamp