Thorn Graph-X Universal Photoprinting Lamp

The Graph-X is a high wattage ultra-violet reflector lamp, created by Thorn's Eric Beeson in the late 1960's. It was developed following a programme of experimentation to determine which metal halide salts would be of most use for the creation of improved metal halide lamps, and some of these materials were found to deliver a spectral output that was suited to lamps for non-lighting applications.

This lamp is based on the iodides of gallium and iron which together, radiate strongly in the blue and UV-A regions of the spectrum. A wide band of radiation between 315nm and 420nm is emitted which makes its output particularly suited to the fields of photo-printing, graphic arts, photo-resists, diazo photopolymer reproduction and other materis. The stippled front lens homogenises the light and gives an elliptical beam distribution measuring approximately 24" x 36" at a distance of 2/3 feet infront of the lamp.

It is intended for operation at either 400 or 1000 Watts (or 400 / 800W in some older units which made use of an earlier lamp that was not rated for such high loading). Lamp life is quite short and electricity consumption rather high at full power, and the lamp takes a minute or so to run up to this level. A system was developed which simmers the lamp at 400W, and when switched to the higher power the response in output is immediate, thus saving electricity and lamp life.

This so-called Graph-X Universal replaces two earlier Thorn lamps, the Graph-X 420 and the Graph-X 365 which had spectral outputs peaking at those wavelengths respectively. The Universal lamp covers both wavelength ranges.
Manufacturer: GE-Thorn Lamps Ltd.
Lamp Power: 400 / 1000 Watts
Lamp Current: 4.6 Amps @ 400W 8.7 Amps @ 800W
Lamp Voltage: 95 Volts @ 400W 100 Volts @ 800W
Cap: Spade terminals
Bulb Finish: Half Aluminised Borosilicate
Bulb Type: PAR-64 (202 mm)
Overall Length: 110 mm
Light Centre Length: Arc tube 10mm behind seating plane of reflector
Electrodes: Backwound thoriated
Atmosphere: Inner: Ar | Hg (Ga,Fe)Ix Outer: Nitrogen
Luminous Flux:
Luminous Efficacy:
Colour Temperature & CRI: CCT: CRI:
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Universal
Rated Life: 1000hrs @ 400W 400hrs @ 800W
Warm Up / Re-strike Time 1000W:1min/800W:2min 7-10mins/2-3mins if cooled
Factory: Leicester England
Date of Manufacture: February 1993 Date Code: 38
Original / Present Value:
References: 1) Thorn Lighting Comprehensive Catalogue, UK, 1984/85, p.233