Mazda Bayonet Capped Halophosphate Fluorescent

The first generations of white fluorescent lamps were all based on phosphors derived from the green-emitting willemite (zinc orthosilicate), which could be modified with increasing content of beryllium to change its colour through yellow to orange. This was blended with blue-emitting magnesium tungstate to create a series of white colours, but with rather low efficacy and useful lifetime.

In 1942 Osram-GEC of England made the most important development in the history of the fluorescent lamp since its invention, with the discovery of the calcium halophosphate range of phosphors, activated with antimony and manganese. By adjusting the Sb:Mn ratio the colour could be tuned from a broad blue to broad orange emission, with several shades of white in between.

The original halophosphate materials delivered approximately 30% more light than their silicate predecessors, along with the achievement of a higher quality white light that was closer to the blackbody locus. Another advantage was the possibility to achieve white light from a single phosphor, avoiding the batch variations from blending the earlier mixtures. Still another advantage was the dramatically lower production cost of the halophoshates. But perhaps most important of all was their safety. Following a number of deaths at America fluorescent lamp plants, it was established beyond all doubt in 1947 that the beryllium phosphors were fatally toxic to some individuals, and their use was outlawed. GEC placed its first halophosphate lamps on the market in 1946, copied quickly by its British competitors - and following the revelations of the toxicity of beryllium, the entire world's fluorescent business swiftly adopted the GEC halophosphate materials.
Manufacturer: The British Thomson-Houston Co. Ltd.
Lamp Power: 80 Watts
Lamp Current: 0.87 Amps
Lamp Voltage: 100 Volts
Cap Type: B22d/25x26 Brass + Vitrite
Bulb Type: T-38 T-12 in eighths/inch
Bulb Finish: Daylight 3Ca3(PO4)2.Ca(F,Cl)2:Sb,Mn
Electrodes: Coiled-Coil + Anode Plates Triple Carbonate emitter
Discharge Length:
Atmosphere: Hg | Ar
Luminous Flux: 3,600 (@ 100h)
Luminous Efficacy: 45 lm/W (@ 100h)
Colour Temperature & CRI: CCT: ~4000K CRI: ~Ra 50
Chromaticity Co-ordinates: CCx: CCy:
Rated Lifetime:
Warm-up & Re-strike Time: 1 minute Instant
Burning Position: Universal
Nominal Length: 1524 mm 60 inches
Factory: Leicester England
Date of Manufacture: August 1949 Date Code: 2892
Original Value: £0 15s 0d (1950)
References: 1) BTH-Mazda Lamp Catalogue, UK, 1950, pp.10-11
2) Metrovick Lamp Catalogue, UK, 1947, pp.12-13
3) Thorn Lighting Comprehensive Catalogue, UK, 1969
4) The GEC Research Laboratories 1919-1984, R.Clayton & J.Algar, publ. Peter Pereginus 1989, ISBN 0 86341 146 0, pp.79-80 & 87-92
5) Lamp Phosphors, H.L.Burrus, publ. Mills & Boon 1972, ISBN 0 263 05133 1, pp.9-13
6) Revolution in Lamps, R.Kane & H.Sell, publ. Fairmont Press 2001, ISBN 0 88173 351 2, pp.97-99