On Fri, 13 Jan 2006 20:01:23 GMT, WM
wrote:

Here in the UK, at my local Tesco supermarket I saw some GLS bulbs
which has a glass envelope that were slightly smaller than usual.

What's the idea behind this?

As "meow" said, it saves material, reduces shipping and
storage costs and allows more lamps to be placed in a given
area of shelf space.

Wouldn't a 100W filament make a smaller bulb glass envelope get
hotter than the larger standard envelope.

Yes.

And therefore wouldn't this make the life shorter?

Yes - if the lamp is not properly processed. 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.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.