Melted bulb

[Zukipilot]

Thought I'd share something interesting. I have seen blown bulbs before, but never anything like this.

[urbanzook]

wow an how did that happen

[Tonka]

Sometimes the bulb goes when the bit thats broken moves. It sometimes lights up again and could be close to the glass, which will heat it up and change its shape.
Thats my theory

[dan_2k_uk]

my guess would either be a hotspot on the glass created by a bit of grease on it when it was fitted or the halogen gas got out causing the filament to glow very brightly and hot for its last few seconds of its life.

90% of a filament lamps energy used is given of as heat (wasted) so when it goes it goes hot

[urbanzook]

so thats wot happens when you touch the glass.

[dan_2k_uk]

yep. had a load of those halogen downlight lamps at work and some of them popped the glass off the front and melted little disc shapes into a brand new carpet!

[Zukipilot]

Still not sure how it happened as I have a habit of wiping the glass with a piece of clean paper towel so there should be no grease or oil on the glass.

Still interesting to see how much heat is given off by the bulb though.

[dan_2k_uk]

usually once its been touched it kills them wether you wipe it off or not.

its because small particles of the filament fly off as it heats up and then the Halides (halogen gas particles) pick up the particles and return them to the hottest part of the lamp (usually the filament)

this is why halogen lamps have a average life of 2000 hours where as a normal argon filled lamp has a lifetime of around 1000 hours.

unfortunatly when the quartz has even the tinyest bit of grease on it it creates a hotspot thus attracting some of the Halides carrying particles of the filament to it. this obviously starts a never ending chain reaction of the filament wearing out quicker and the hotspot getting bigger and hotter which in turn magnifies the effect so it gets bigger and hotter again and again and again and again and again and again and again and again and again etc... etc.... untill either the filament gives way or the hotspot on the quartz totally fails

im sure you get the point


hope that makes some sense.

[trotter]

never knew u were such a light bulb geek dan

[urbanzook]

check you with the buld insite dan