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?

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

And therefore wouldn't this make the life shorter?

In article ,
WM writes:
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?

I don't know. Philips have started making theirs smaller.
These smaller GLS lamps won't fit into a number of fittings
my parents have because the neck is too short.

I wonder if GLS lamp sizes are covered by a British or EU
statndard?

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

And therefore wouldn't this make the life shorter?

There are loads of factors which affect lamp life.

--
Andrew Gabriel

In uk.d-i-y 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?

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

And therefore wouldn't this make the life shorter?

No.
You simply increase the filliment thermal conductivity to the outside,
by various means - usually the problem is isolating it from the
environment - making the filliment cooler is easy.

I don't know exactly what this will do to efficiency, it's horribly
complex.

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?

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

And therefore wouldn't this make the life shorter?

It reduces the amount of material used, and the energy needed to
produce that material. It also reduces the amount of energy used in
transport, and the amount of material in landfill. And finally less
shelf space equals space for another line. So its more efficient all
round. I presumed those were the reasons for doing it.

Golf ball bulbs are the other option for lower wattages, but not 100w.


NT

In uk.d-i-y wrote:
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?

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

And therefore wouldn't this make the life shorter?

It reduces the amount of material used, and the energy needed to
produce that material. It also reduces the amount of energy used in

And increases the possibility of fires.
I _think_ that given a constant life - that the bulb will be less
efficient.

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
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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.

"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

On Sat, 14 Jan 2006 12:34:03 GMT, WM
wrote:

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?

No. I was talking about contamination INSIDE the bulb. Your
oil is on the outside. The glass keeps air out so it will
obviously keep oil out :-) Now, if you completely cover
the lamp with a thick enough layer of oil or any other
material so that an insulating layer is formed AND the lamp
was not properly processed so that it has residual
contamination, then - perhaps.

--
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.

On Fri, 13 Jan 2006 19:48:08 -0500, Victor Roberts
wrote:


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.

Let me clarify my own statement.

The lamp life will be shorter only if there is contamination
such as oxygen or compounds of oxygen such as water vapor on
the inside glass wall or buried in the glass wall very close
to the inside surface. When the bulb temperature is
increased THIS contamination can be released into the bulb
environment and oxidize the filament.

--
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.