On 14/01/2019 11:02, Thomas Prufer wrote:
On Mon, 14 Jan 2019 10:31:56 +0100,
(D.M. Procida) wrote:

I assume it would not come to any harm run at a lower voltage, though I
know that some lamps can darken as the result of deposits on the inside
of the glass when run dimmed.

The darkening is metal vaporizing from the filament and settled on the glass.
The bulbs that habe a mechanisnm to avoid this are the halogen bulbs: the glass
is run hot, a halogen scrubs the metal off the glass, and re-deposits it on the
filament.

This is positively not a halogen bulb -- run it with as low a voltage as you
like.

The lifetime of a lightbulb is exquisitely sensitive to to voltage, something
like (voltage/ratedvoltage)^-12 to (voltage/ratedvoltage)^-14. So running a bulb
at 99% of the rated voltage will increase its life by 12-15%.


Thomas Prufer


When I moved to my current house in 1991, the bathroom had one of those
nasty fittings with three 40-watt reflector bulbs that gave out rubbishy
illumination.

I replaced it with a standard BC fitting and stuck in a 60-watt clear
Woolworths bulb as a temporary measure so I could see what I was
doing when shaving. (bulb marked 240 volts).

It's still there and working fine.