Thorn 2D Compact Fluorescent (Half Coated)

In the late 1960's Thorn Lighting, new owners of the AEI Mazda group of companies, ceased development of the troublesome 'Panel F' flat fluorescent lamp which had been developed jointly with GE of America but was never marketed in Europe. Research subsequently investigated the possibility of bending glass tubes into a shape that would give a square illuminated area with the greatest efficacy and ease of manufacture. Some fifteen years later the solution was commercially realised with the announcement of Thorn's pioneering 2D compact fluorescent lamp - shown here in a special half-coated demonstration version.

The first version was this 16W product, launched in 1983, and with a 5000 hour service life and 900 lumen output it was directed specifically at replacing GLS incandescent lamps. A magnetic ballast equipped with bayonet cap on one side and 2D lampholder on the other enabled the 2D to go into ordinary domestic lighting fittings wherever the larger lamp diameter could be accommodated. In addition the 2D gave tremendous freedom to luminaire designers who could create compact slim lighting fittings for surface mounting on ceilings and walls with a very low profile.

Incorporated inside the plastic base is a glowbottle starter to simplify the required control circuitry. A later long-life version was also offered with a rapid-start internal electronic starter. Following the success of this lamp a larger 28W size was offered for commercial applications based on the new generation of slim luminaires that the 2D lamp permitted. A 38W rating, offering as much light as a 4-foot fluorescent tube was an important addition to the range, which is now complete with small 10W and 21W alternatives.
Manufacturer: Thorn EMI
Lamp Power: 15.5 Watts
Lamp Current: 0.20 Amps
Lamp Voltage: 97 Volts
Cap Type: GR8
Bulb Finish: Triphosphor 827
Bulb Type: T-13
Dimensions: 135 x 135 5¼ x 5¼ inches
Thickness: 27 mm 1 1/16 inches
Discharge Length:
Electrodes: Triple Coil Tungsten Triple Carbonate Emitter
Atmosphere: Ar, Kr | Hg
Luminous Flux: 1,050 lm @ 100 hours 925 lm @ 2000 hours
Luminous Efficacy: 67.7 lm/W @ 100 hours 59.7 lm/W @ 2000 hours
Colour Temperature & CRI: CCT: 2800K CRI: Ra 82
Chromaticity Co-ordinates: CCx: 0.460 CCy: 0.414
Burning Position: Any except with U-bends below cap centre
Rated Lifetime: 5,000 hours Rated to 50% survival
Warm-up / Re-strike Time: 2 minutes Instant re-strike
Factory: Enfield, London United Kingdom
Date of Manufacture: August 1983
Original / Present Value: £5.63 (1988) £10.11 (2005)
References: 1) Thorn Lighting Comprehensive Catalogue, UK, 1983, p.108
2) Thorn Lighting Price List 1988.