The Lamp Room

I have a 70W double ended MH as a daily light source in my bedroom. When the lamp had worked up a few hours it started to show pink flashes as it gets to the end of its warm up this lamp is branded as a 'TCP' and has done 18 months so far. The only other halide I've seen do this was another 70W double ended but an Osram (at my Primary School). How common is for halides to flash pink as they reach the end of their warm-up?

I've seen CDM-T's do this also from GE & Philips.

I find this happens when the halide salts melt and touch an electrode.

This is called flaring, and exactly like Jonathan says is caused when a droplet of halide is suddenly vaporised - its colour momentarily overpowering the blueish merciry spectrum with its pinkish colour light.

In some poorly made lamps, especially when burned with the arc tube vertically, it can occurr repeatedly. If there is a small cavity around the electrodes the halides may condense there, until the droplet is big enough that it falls under gravity and causes a pink flare. It mainly happens in 400W cap-up quartz lamps, and very low wattage quartz types.