Royal Ediswan Tubular Sintered Tungsten

The original tungsten lamps were developed in Germany under Auer (Osram), and in Austria/Hungary under Just & Hanamann (Tungsram). Production was quickly established in Britain by Sir Hugo Hirst, chairman of the British General Electric Company, thanks to his close ties with Germany as an immigrant of that country. However its principal competitor, Royal Ediswan, was relatively late to enter this business and is not believed to have commenced metal filament lamp production until around 1910.

Ediswan had formerly benefitted from its monopoly over the British lamps market, and failed to invest in new lamps : there was little incentive for a company with near-100% market share to improve its products when there was in effect no competition. However the considerably more competitive conditions on the continent were driving forward innovations in improved lamps based on metallic filaments.

It is not clear how Ediswan acquired rights to make sintered tungsten lamps in Britain. Its major competitor Osram-GEC was the first company to acquire an exclive license for these types with the German and Hungarian inventors, as was repeated in Holland by Philips, and in the USA by General Electric. It is suspected that even at this time, Ediswan may have enjoyed a patent licensing agreement with Philips, the latter having taken over a significant shareholding in Ediswan in 1919-20 (although in 1924-25 Ediswan was later acquired by BTH, a 100% subsidiary of GE).

The lamp construction appears similar to other sintered tungsten lamps in most aspects, except the upper supports which are fabricated from coiled loops of flat metal strip.
Manufacturer: Royal Ediswan
Lamp Power: 17 Watts
Lamp Voltage: 105 Volts
Lamp Current: 0.162 Amperes
Cap Type: B15d Brass + vitrite
Bulb Type: T-25 T-8 in eighths/inch
Bulb Finish: Clear Soda-lime glass
Filament Type: 5S-2 Squirrel Cage
Atmosphere: Vacuum
Luminous Flux: 201 lumens
Luminous Efficacy: 11.8 lm/W 1.06 WPC
Luminous Intensity: 16 British CP
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2400K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.486 CCy: 0.415
Rated Lifetime: Approx. 800h
Burning Position: Universal
Overall Length:
Light Centre Length:
Factory: Ponders End England
Date of Manufacture: November 1911 Date Code: 3023
Original Value: GB £0 3s 6d (1910)
References: 1) Royal Ediswan Lamp Catalogue, UK 1910
2) Anatomy of a Merger, R.Jones and O.Marriott, publ. Pan Books of London (ISBN 0 330 23213 4), 1970, p.21.