S-1 Sunlight Mercury Discharge

In 1929 GE unveiled this very successful new lamp, the S-1 Sunlight. It was conceived by Royal Strickland and Matthew Luckiesh to deliver a spectrum having a mild ultraviolet content resembling that of the sun. It was believed that irradiating people with this light would give them vitality and maintain health. It replaced the earlier "CX" incandescent lamps that had been developed for a similar purpose.

It is a most unusual kind of hybrid incandescent-discharge source. The bulb is is of a special UV-transmitting hard glass, and is filled with an enormous quantity of liquid mercury plus low pressure argon. It contains a V-shaped tungsten filament, whose ends have extra windings to increase their thermal mass such that they can function as electrodes without burning out. When illuminated on a low voltage transformer, the filament lights and thermionic emission takes place. As the mercury begins to vaporise and the gasfilling becomes more conductive, a glow discharge is formed, which gradually transforms into an arc across the ends of the filament, ballasted by the external transformer. The filament continues to decrease in intensity as the arc draws more current, but remains lighted at all times. The filament produces a warm white light plus infrared radiation, while the mercury arc contributes ultraviolet rays.

These lamps were normally employed with a separate wide-beam reflector to complement the lighting in any room of the home, and were also used in offices and hospitals. In 1937 the S-1 was joined by the smaller S-2. Both were initially produced with clear glass, but owing to the high brightness of the arc, from 1939 onwards they changed to the inside frosted pearl bulb illustrated here.
Manufacturer: General Electric Co. of U.S.A.
Lamp Power: 400 Watts
Lamp Current: 30 Amps 9.5A at starting
Lamp Voltage: 14 Volts Approx. 30V at starting
Cap: E39s/41 Ni plated brass
Bulb Finish: Inside Frosted #776 borosilicate glass
Bulb Type: PS-70 PS-22 (in eighths/inch)
Overall Length: 163.5 mm 6 7/16 inches
Light Centre Length: 127.0 mm 5 inches
Electrodes: C-2V Overwound plugged tails
Atmosphere: Argon 0.9 atm. during operation
Luminous Flux: 7,200 lm @ 100 hrs
Luminous Efficacy: 18.0 lm/W @ 100 hrs
Colour Temperature & CRI: CCT: CRI:
Total Ultraviolet Output: 68,000 E-Vitons
Burning Position: Vertical base up to horizontal
Rated Life: 400 hours 50% survival, ~100% UV flux
Warm Up / Re-strike Time: 5 minutes to full output Instantaneous restrike
Factory: Nela Park, Ohio U.S.A.
Date of Manufacture: Circa 1950
Original Value: US $4.75 (1948)
References: 1) GE Lamp Catalogue, U.S.A., 1948, p.30
2) GE Brochure, Sunlight Mazda S-Lamps & Mercury Mazda H-Lamps, Prices & Essential Technical Data, U.S.A., 1939
3) GE Brochure, Mercury Lamps - Operating Characteristics & Applications (Bulletin LS-103), U.S.A., 1947
4) GE-Mazda Lamps - Characteristics & Applications (Bulletin LD-1), C.E. Weitz, General Electric U.S.A., 1939
5) Simulating Sunlight, M. Luckiesh, General Electric Review v.33 no.5, May 1930, pp.283-295
6) Ultra-Violet from the Sun and from the General Electric Sunlamp, N.T. Gordon & F. Benford, General Electric Review v.33 no.2, February 1930, pp.89-91
7) Biography of Royal Strickland
8) Biography of Matthew Luckiesh
9) US Patent 2,047,042 - Enclosed Arc Device, R.F.Strickland (General Electric USA>, Filed 1929-Nov-18
10) US Patent 2,081,776 - Enclosed Arc Device having improved electrodes (S-2), R.F.Strickland (General Electric USA), Filed 1931-May-19
11) US Patent 2,104,680 - Enclosed Arc Device having improved UV flux and starting, R.F.Strickland (General Electric USA), Filed 1931-Feb-25