Westinghouse Tantalum Filament of American Design

Soon after the invention of the tantalum lamp in Europe, news of the breakthrough caused great concern among the American manufacturers, who had performed no significant research of their own on metal filament incandescent lamps. The risk of losing their dominance to superior imported lamps was high, especially for General Electric, which together with its National subsidiary operated a near-monopoly of the American market.

In 1904 Siemens & Halske offered GE the American rights to its invention for a high price, but GE declined owing to the reduced life of tantalum filaments on AC circuits. However such was the level of threat that GE eventually conceded, and on 10th Feb. 1906 for a payment of $250,000, secured exclusive American rights for itself and National to produce the lamps on a royalty basis. All American-made lamps were produced with tantalum wire sourced from Berlin.

Westinghouse, America's second largest manufacturer and the brand name marked on this lamp, was not included in this exclusive deal. It is not known whether Westinghouse might have secured the rights to manufacture its own tantalum lamps at a later date - if not, then this lamp was most likely manufactured for that company by GE. Despite this limitation, many of the American-made tantalum lamps are in fact branded Westinghouse, and it is evident that the company still achieved considerable success. Many of them are like this example, marked with a label indicating their application in the "Mirroscope", an early form of projection device. It is presumed that the compact filament, high brightness and whiter light made tantalum lamps eminently more suitable than carbon types for this application.

Manufacturer:	Westinghouse
Lamp Power:	50 Watts
Lamp Voltage:	120 Volts
Lamp Current:	0.417 Amperes
Cap Type:	E26s/25	Brass + vitrite
Bulb Type:	SA-58	SA-18 in eighths/inch
Bulb Finish:	Clear	Soda-lime glass
Filament Type:	S-1	Squirrel Cage
Atmosphere:	Vacuum	Red P Getter
Luminous Flux:	275 lm	24 CP
Luminous Efficacy:	5.5 lm/W
Beam Intensity:	N/A
Beam Distribution:	N/A
Colour Temperature & CRI:	CCT:2300K	CRI:Ra100
Chromaticity Co-ordinates:	CCx: 0.495	CCy: 0.413
Rated Lifetime:	Approx. 1000h on DC	300-500h on AC
Burning Position:	Universal
Overall Length:	127 mm	6 inches
Light Centre Length:	83 mm	3¼ inches
Factory:	Central Falls, R.I.?	U.S.A.
Date of Manufacture:	1907-1910
Original / Present Value:	Unknown	Unknown


References:	1) American Tantalum Filament Lamps, website of Ed Covington (Web Archive)
	2) Photometric measurement