Cracking pic that

Think i prefer the gec arc tube design to thorns like.

I agree, even though the Thorn design is better, the G.E.C design *looks* better

I do love staring at quality designed lamps. I love the design of these. no wonder my eyes are fucked lol

I must say I prefer the GEC ones myself, but I do love the thorn ones. Fascinating low pressure sodium lamps to watch warm up. They beat BC cap sox

Great photo, it really captures well one some of the physics behind discharge lamps, known as Ionic Pumping. During use there are of course many free electrons in the centre of the discharge tube, and these negatively charged particles repel the positively charged sodium ions towards the wall of the discharge tube. The result is that most of the sodium yellow light is generated close to the glass wall, which shows up perfectly in this photograph. If it wasn't for this effect, LPS lamps would not exist. Since sodium vapour absorbs its own radiation, if the yellow light was created at the centre of the discharge tube instead of the surface, much of it would not be able to escape, and lamp efficacy would be far too low to make them commercially interesting.

Its like a lava flow!

Thanks for the info James. You learn something new every day. I do love watching low pressure sodium lamps warm up.

How unusual to see a GEC arc tube in a Thorn lamp??? Still, makes it look better than it would with the Thorn version installed. Might be less efficient, but way more interesting to watch warm up!