Lighting Here and There

This lamp is the only really old lamp on this site. It is a Crompton 250W 250V type MA/V lamp (actually NOS), from the late 1950s. It has a large (about 4 inch long) glass arc tube, compared with the more modern 'MB' type lamps which have a smaller quartz arc tube. This lamp has to be burned vertically, base up, otherwise the arc would bow upwards and damage the arc tube.

In these pictures I've compared it with a modern Thorn 250W MBF/U mercury fluorescent lamp. The old lamp has exactly the same electrical characteristics as the modern MBF lamp of the same wattage so I was able to use an ordinary MBF ballast. Notice how long the arc is in comparison! Also you'll notice in the first and third pictures that the colour of the actual arc in the modern lamp, as seen through the phosphor coating, is exactly the same colour as the old lamp. You can also see the shadow of the support wire on the new lamp. I've no idea as to the light output of the old lamp, but it compares very favourably to the modern one.

Here's a closeup of the arc when the lamp is fully warmed up (about 10 minutes). As can be seen from the video the arc is very unstable for the first few seconds, then it settles down into a dim but quite fat discharge. As time progresses (again in this video after the first 30 secs or so time is speeded up- see the clock bottom right of the frame) you can see the arc get brighter and narrower, bending away slightly from the bottom electrode which is now red hot.

The one thing I can't convey here is the smell of this lamp- it smells of the 50's! (if that makes any sense)