My school used to sometimes install T8s into instant start T12 fittings, usually what would happen is both ends would just go orange and not do anything, however if you flicked the switch off and on again, the whole lamp would go pink with the ends getting whiter till the middle eventually went from pink to white after about 10 minutes.

One thing I was quite surprised about is that one of my lecture rooms uses instant start T12 fittings and out of the 10 fittings, about half are actually 'Thorn' branded lamps! Though they look quite worn and the newer ones are badged by Philips.

My lecture room last year had T12s on dimmer switch function.

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"I used to rule the world... Now I sweep the streets I used to own."
Remembering GEC.

I didn't know that flo tubes like the T12 and T8 could be operated on dimmer switches, wouldn't it damage the lamp over time though.

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From streetlighting to radio, dance through the night whilst the streetlights are glowing outside.

I was just thinking the same thing. Fluorescents on conventional control gear shouldn't be operated by leading edge dimmer switches... some modern electronic ballasts can be (I have one for running 2x 36W PL-L lamps - it can be dimmed like this and can even run on 240v DC, making it suitable for Central Battery emergency lighting systems), but in most cases these use 0-10v DC terminals for use with either a BUS control or a suitable dimmer.

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Fluorescent tubes of any type can only be dimmed using suitable ballasts. Indust's lecture theatre must therefore have the necessary control gear to do that. Nothing "new" about this - I first saw dimming T12 over 30 years ago, and my lecture theatre at Uni had dimming T8s.

The T12 fittings are (needless to say) very old with the cases themselves being very bulky and yellow/brown, but nevertheless I'm still quite surprised they exist at the uni, although they seem to install T12s in most suitable fluorescent fittings, moreso than T8s. I doubt it'll be long before the dimmable lights are removed anyway, they seem to be phasing them out from other areas of the uni.

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"I used to rule the world... Now I sweep the streets I used to own."
Remembering GEC.

The fluorescent fitting that I have in my kitchen is the best part of 20 years old and it is worked by a standard switch. I have had to remind my parents that once the T12 tubes gone, thats it, the entire fitting will have to be converted as a T8 tube won't fit.

I do think that dimmer switches will eventually become a thing of the past what with B22 bayonet CFL's unable to dim instead flicker like a candle. I don't know anything about dimable LEDs or if they could be worked on a dimmer switch.

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From streetlighting to radio, dance through the night whilst the streetlights are glowing outside.

There are dimmable domestic energy saver CFL lamps and dimmable LED lamps... but they are more costly than the standard versions, which is just another part of this whole "let's force people to buy more expensive bulbs so we make more VAT" malarky I don't like. The light in my PC room/office is switched by a remote control switch that dims in the bulb to the set brightness so as to prolong coil life... if won't work if I can't get suitable dimmable lamps for it. You also have to be careful with 12v halogen fittings, as some transformers don't like being dimmed and will buzz very loudly.

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My local Asda are selling four-packs of 40w tungsten bulbs at two for £4, bargain! No sign of any such offer on domestic CFLs though and in fact the shelves were dominated by tungsten and halogen lamps when I visited on Saturday! Needless to say I got myself a couple of packs on Saturday (I think domestic CFLs are bobbins) as well as a nifty miniature LED christmas tree for £5 but that's another story  

Still got a load of the free CFL lamps you used to get in the post  

Earlier this year the Asda in Killingbeck were flogging 10 CFL lamps for 50p.

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From streetlighting to radio, dance through the night whilst the streetlights are glowing outside.