I think I have seen worse at the approach to Euston Station. There are what I think are a few remaining greened out 250w mercs which run continuously and these have not been replaced in over 20 years and are about as bright as a 15w incandescent!

Yeah I've seen worse too, seen some lanterns around Camrbridge, particularly down back streets which are dayburning although you can only just make it out and that's when looking directly at the lamp! At night they provide no usable light at all, a tealight would provide more light, seriously!

It's amazing though that they burn for so long! If there was just some way of preventing blackening you'd easily have a lamp that lasts a few decades!

Well, halogen lamps have halogen in (obviously LOL) which prevents the lamp from turning black - would this be a way of doing it? I copyright that idea LOL

Possibly, I would of thought that would of been tried though, perhaps adding iodine to the discharge tube would help! James would know!

Tungsten from the electrodes also causes the inner quartz arc tube to become black. This in turn increasingly absorbes the UV-C rays that makes the fluorescent coating on the outer bulb emit red light. So the red wavelenghts diminish and the light turns to green.

I need to get a snap of that 80w MBF Thorn Precinct bulkhead near me! I'm sure it has the original lamp from when the place was built in 1982! Burning 24/7! I've a good mind to go out with a stepladder and re-lamp it! There are some 250w MBF floods at my work that are starting to take on a green tinge now!

Leave it until next year then it will have done 30 years service! Really though it would be nice to see the state of the lamp after that many hours (years) burning.

Oh yes, if I do get my mitts on that lamp, it's going in the collection! This lamp has been getting progressively dimmer over the years! It was on the wane back in the late 80s/early 90s! I wonder if it will have seized in it's holder after all these years?

Mercury lamps are definitely my favourite but their only disadvantage is that they just go on forever even when they become less efficient than a carbon heater lamp and some people only change lamps when they just don't work at all.

I don`t have a night shot of these, but theres 4 of them, and their beyond `greened out`

i saw one in Birmingham that was barely giving any light out.

When i was in birmingham i saw a 80W merc that was so dim there wasnt hardly any light emmiting from it. the bowl was clear, and the lamp was glowing that dimly you couldnt see the internals. if its still there (which it should be - its private) i'l try and snap it.

Is this as bad as our aforementioned 80w Precinct Paul?

Actually, there were ways of preventing blackening. Westinghouse had the LifeGuard line of lamps, which used a special emitter material which turned the arc tube a milky white instead of black. Over years they would cloud up but lumens wouldn't drop off a cliff like on traditional lamps. Anecdotal evidence from some older collectors / people that worked in the industry state cases of lifeguards lasting 20,30,40 years still giving reasonable brightness. Unsurprisingly when Philips took over Westinghouse the quality of lifeguard lamps dropped off a cliff and that, as they say, was that.