Pollard Lamp with Silver Film Seals

During the early 1890s some particularly novel forms of incandescent lamps appeared on the market as manufacturers tried to circumvent the Edison patents. One of these was the lamp invented by Edward Pollard in 1892, whose design differs from the Edison patent by eliminating the usual metal wires that are sealed through the bulb.

Pollard was a glass etcher living in Cambridge (MA), and he developed a technique of applying electrically conductive films to glass surfaces. According to his Patent, he created finely powdered silver by dissolving the same in nitric acid followed by precipitation after addition of copper pieces. This was collected and after sieving and washing, blended with two parts copaiba balsam and one part fir balsam to form a paste. The paste was printed in two wide strips along the inner surface of a glass tube, and baked to drive off the binder and form a strong bond between the silver and glass.

One end of the glass tube was then pinch-sealed around a pair of iron wires, the filament later being attached to their free ends - the silver films thus carrying the current into the bulb without use of any metallic wire. Contact to the outside part of the films is effected by copper wires, pressed into contact against the films by a cork wedged into the stem.

Pollard did not make lamps himself but licensed his patent to lampmakers facing problems as a result of the Edison litigation. Owing to the similarity of this lamp with that in other collections which bear a label, it is believed that it was made by the Packard Company of Warren OH. Other possibilities are Buckeye of Cleveland OH, the Boston Incandescent Lamp Co., and the Imperial Electric Mfg. Co.

Manufacturer:	Packard?	(The New York & Ohio Co.)
Lamp Power:	Approx 90 Watts
Lamp Voltage:	100 Volts
Lamp Current:	0.9 Amperes
Cap Type:	Thomson-Houston small	Fibre Insulator
Bulb Type:	P-60	P-19 in eighths/inch
Bulb Finish:	Clear	Soda-lime glass
Filament Type:	Squirted Cellulose	Deposited joint
Atmosphere:	Vacuum	No getter
Luminous Flux:	201 lm	16 Candle Power
Luminous Efficacy:	2.2 lm/W	5.6 Watts per Candle
Beam Intensity:	N/A
Beam Distribution:	N/A
Colour Temperature & CRI:	CCT: Approx. 2000K	CRI: Ra 100
Chromaticity Co-ordinates:	CCx: 0.527	CCy: 0.413
Rated Lifetime:	Approx 800 hours
Burning Position:	Vertical only	(to avoid filament sag)
Overall Length:	140mm	5¼ inches
Light Centre Length:	82mm	3¼ inches
Factory:	Ohio Lamp Plant, Warren	U.S.A.
Date of Manufacture:	c. 1892-1894
Original / Present Value:	Unknown	Unknown


References:	1) The Pollard Lamp, The Incandescent Electric Lamp 1880-1925, E.J. Covington, NELA Press, 1998 p.115.
	2) The Lamp of Edward Pollard, Early Incandescent Lamps website, E.J. Covington (Web Archive).
	3) Packard-Pollard Lamp of 1893, Past Technology Collection.
	4) US Patent 485478, E. Pollard, Incandescent Electric Lamp, Nov. 1 1892.