Thorn SON-R Reflector 70W
Considering the popularity of reflector-type High Pressure Mercury lamps, it was perhaps a logical development to extend similar principles to the High Pressure Sodium lamp. The first such lamps were introduced in high wattage ratings for industrial lighting by Osram-GEC in 1976, however the design never became especially popular for the reasons explained on that page. GE of America followed suit with a 70W lamp in large R125 bulb for outdoor floolighting applications, and Westinghouse of USA developed another 70W lamp in a dichroic PAR38 envelope to provide a cool light source for the illumination of coal mines, but neither were a great success.

Thorn Lighting instead attacked the commercial interior lighting market, and in 1980 launched this 70 watt lamp in the much more compact R-95 bulb, making it the smallest diameter high pressure sodium reflector lamp ever commercialised. Because of the axially mounted arc tube within an aluminised bulb, a remarkably tight beam with excellent optical control is achieved.

It found favour in certain interior locations which demand high lighting levels and low operating costs, but where colour rendering is not of paramount importance. Typical applications include low-profile ceiling downlight luminaires in such places as corridors or wherever all-night interior security lighting is called for, where the integral reflector permits small and discreet installations. Today it has been largely superseded by compact fluorescent lamps in recessed ceiling luminaires, which can provide very nearly the same light intensity at high efficacy, but with a white light which is generally more desirable in such applications.
Manufacturer: Thorn Lighting Ltd.
Lamp Power: 70 Watts
Lamp Current: 0.98 Amps
Lamp Voltage: 90 Volts
Cap Type: E27s/27 Ni plated brass + vitrite
Bulb Type: R-95 R-30 in eighths/inch
Bulb Finish: Pearl aluminised Soda-lime glass
Electrodes: Backwound Tungsten BCT Emitter
Atmosphere: Na20:Hg80 | Xe 25 torr Outer: Hard Vacuum
Luminous Flux: 4,000 lm (@ 100h) 3,700 lm (@ 2000h)
Luminous Efficacy: 57.1 lm/W (@ 100h)
Luminous Intensity: 6,400 candelas
Beam Distribution: 24° to 50% peak
Colour Temperature & CRI: CCT: 2000K CRI: Ra 35
Chromaticity Co-ordinates: CCx: 0.542 CCy: 0.415
Lifetime: 10,000 hours 90% flux & 85% survival
Warm-up & Re-strike Time: 10 minutes <1 minute
Burning Position: Universal
Overall Length: 144 mm 55/8 inches
Factory: Leicester England
Date of Manufacture: September 1982 Date Code 09
Original Value: GB £27.73 (1988)
 
References: 1) Thorn Lighting UK Catalogue, 1987/88.
2) Thorn Lighting UK Price List, 1987.
3) Thorn Lighting Product Data Sheet 70W SON-R 96-8095A, 12-4-1984 (including referenced 1980 predecessor).
4) Thorn Lighting SON Manufacturing Specifications.
5) A Decade of SON, D. Peach, Thorn Lighting Journal No 22, pp.3-5.