"WM" wrote in message
...
On Sat 14 Jan 2006 00:48:08, Victor Roberts xxx@lighting-
research.com wrote:

There is a test
called the "slumper can test" used in the lamp industry to
check for processing contamination. A closed metal can is
placed over an operating incandescent lamp. This heats the
glass to higher than normal operating temperature. If the
lamp is not clean then the higher glass temperature will
drive contaminants such as water vapor out of the glass
bulb, the filament will crack the water into hydrogen and
oxygen and the oxygen will combine with the tungsten,
causing the lamp to have shorter than normal life.


Does this mean that when I smear the bulb of my bedside light with
aromatic oil such as bergamot (to make the smell diffuse into the
room) then I am *noticeably* shortening the life of the bulb?

I'm not worried about a 3% or 4% reduction in life

But a shorter life by 15% or 20% is another thing.

No, not unless the glass bulb cracks (fractures). Vic, I believe, was
talking about a chemical process -- like cracking petroleum to make oil and
gasoline.

It's commonly believed, but not true, that a hotter bulb means shorter lamp
life. As Vic said, if the lamp is made properly there's no relationship.

Lamp manufacturers have been moving toward smaller bulbs for some years for
the reasons that others have mentioned. Once, all NA 100 watt lamps were
"A-21" or 21/8 inches in diameter. Now, they are A-19 and some are smaller.
There is a risk, of course, that higher bulb temperatures will increae the
incidence of fire in portable lamps with flammable shades or if someone puts
a high-wattage lamp into a socket intended for a lower-wattage lamp.

Terry McGowan