HQLG 400-01 'Goldweiß' Mercury Discharge

Narva manufactured three distinct types of coated mercury discharge lamp, all under the generic German name HQL to signify a high pressure mercury fluorescent lamp. The three colours offered were HQLS Silberweiß (silver white), HQLG Goldweiß (warm white), and HQLD Deluxeweiß (deluxe).

A spectral scan of this lamp reveals the characteristic twin deep red peaks of magnesium fluoro-germantate, thus identifying the phosphor type employed here (the vertical axis of the lower spectral distribution is magnified 20x to more clearly illustrate the phosphor emission). This was the first mercury lamp phosphor to achieve widespread success, having been invented by Westinghouse in 1950. Although it phosphor generates a significant amount of red energy, it is at such a long wavelength as to be at the edge of the sensitivity of the human eye, and is thus not so effective as might be suspected from the charts below.

Magnesium fluoro-germanate is an excellent absorber of longwave UV radiations, making it an efficient phosphor for high pressure mercury lamps, but its absorption curve also extends into the blue end of the visible spectrum. Thus it absorbs some of the blue mercury lines and causes total light output to fall. Additionally the loss of blue light leads to a proportionally stronger mercury green line, and although these lamps have a higher red ratio of around 6%, the light appears slightly greener than from uncoated lamps.

In addition to this lamp, Narva offered the Silberweiß colour having an orthophosphate coating for high efficacy but reduced red. Both were superseded by the Deluxeweiß vanadate lamp providing more red and higher luminous flux.
Manufacturer: VEB Berliner Glühlampenwerk
Lamp Power: 400 Watts
Lamp Current: 3.25 Amps
Lamp Voltage: 140 Volts
Cap Type: E40s/45 Ni plated brass + porcelain
Bulb Finish: Mg4(F)Ge06:Mn4+ phosphor Borosilicate hard glass
Bulb Type: BT-120 BT-37 in eighths/inch
Overall Length: 227 mm 9 inches
Light Centre Length:
Arc Length:
Electrodes: Backwound tungsten Double carbonate emitter
Atmosphere: Inner: Hg | Ar Outer: Nitrogen
Luminous Flux: 20,500 lm (@ 100 hours)
Luminous Efficacy: 51.3 lm/W (@ 100 hours)
Colour Temperature & CRI: CCT: 4600K CRI: Ra20, Red Ratio 5.8%
Chromaticity Co-ordinates: CCx: 0.365 CCy: 0.408
Burning Position: Universal
Rated Lifetime: 8,000 hours Rated to 70% survival
Warm-up & Re-strike Time: 4 minutes 5 minutes
Factory: East Berlin East Germany
Date of Manufacture: 1971
Original & Present Value: Unknown
References: 1) Narva Hochdruckentladungslampen, 1970.
2) Spectral measurements.