S-2 Sunlight Mercury Discharge

In 1932 GE's Lighting Headquarters at NELA Park unveiled a most unusual light source to the world. It was the S-1 Sunlight lamp, conceived by Matthew Luckiesh to deliver a light output closely resembling that of the sun. His goal was to develop a light source with the same mild ultraviolet content as natural sunlight, in the belief that irradiating people with this light would give them vitality and maintain health. Judging from the spectacular sales of the lamp, the public seemed to believe this marketing as well!

The S-1 was a large 400W source intended for general irradiation in public areas etc., and a smaller domestic source was soon in demand for residential use. Thus in 1937, this smaller S-2 product was launched. Initially it had a clear glass bulb, but owing to the high intrinsic brilliancy of the lamp which was used at short range domestically, from 1939 onwards it was only made in the inside frosted pearl bulb. The S-1 also changed to frosted glass at this time.

The lamp consists essentially of a V-shaped tungsten filament with heavy windings around the filament tails to increase the thermal mass here. It is sealed inside a UV-transmitting glass bulb which contains a sizeable pool of liquid mercury and low pressure argon. When illuminated on a low voltage high current transformer the filament lights and thermionic emission takes place. An arc gradually builds up across the ends of the filament drawing more current, and as the filament partially reduces in intensity the arc steadily builds up and radiates UV light from the ionised mercury vapour. Lamps are for base up operation only, the purpose of the metal cap being to raise the temperature of the mercury pool and increase the UV output.

Manufacturer:	General Electric Co. of U.S.A.
Lamp Power:	130 Watts
Lamp Current:	8.5 Amps	2A at starting
Lamp Voltage:	15 Volts	30V at starting
Cap:	E29s/30	Admedium Brass
Bulb Finish:	Clear hard glass	Transmitting to 280nm
Bulb Type:	PS-54	PS-17 (in eighths/inch)
Overall Length:	122.5 mm	4 7/8 inches
Light Centre Length:	95.25 mm	3 3/4 inches
Filament:	C-2V	Overwound plugged tails
Atmosphere:	Argon	0.9 atm. during operation
Luminous Flux:	1,600 lm	@ 100 hours
Luminous Efficacy:	12.3 lm/W	@ 100 hours
Total Ultraviolet Output:	8,000 E-Vitons
Burning Position:	Vertical base up to horizontal
Rated Life:	300 hours
Warm Up / Re-strike Time:	8 minutes to full UV output	Instantaneous restrike
Factory:	Nela Park, Ohio	U.S.A.
Date of Manufacture:	December 1939
Original / Present Value:	Not Known


References:	1) GE Lamp Catalogue, USA, 1937, p.27
	2) Weitz, C.E., GE-Mazda Lamps - Characteristics & App. lications (Bulletin LD-1) , General Electric U.S.A., 1939.