If you touch a cold halogen bulb with clean fingers, you ruin the bulb?

Hi Nancy...

'Clean' is a relative term. The fact is, that healthy skin,
even recently cleaned, will produce natural oils, and, in 
the sense that these oils on a halogen bulb will shorten its
lifespan, yes, they can ruin it.

Unfortunately, I could not find an exact explanation of why
this is so, and I'm hoping you'll feel that such an explanation
falls outside of the scope of your question, since a fair amount
of searching didn't turn it up. It appears to have something to
do with the fact that halogen bulbs are made from quartz rather
than glass, or silicon, as are incandescent bulbs. 

The most comprehensive answer I could find was on the 
TekLight site, which manufactures halogen bulbs for 
medical equipment, such as lighted microscopes:

"Why shouldn't I touch my halogen bulb with my fingers?"

"Do not touch the surface of a quartz halogen bulb with
 bare fingers, as the quartz surface will be exposed to
 the salts and oils in the hand. This will cause a weak
 area and lead to premature lamp failure.  If you happen
 to contact the bulb with your fingers, carefully clean
 the quartz surface with a gentle solvent such as alchohol."
http://www.teklight.com/FAQ_s/faq_s.html

Other sites basically repeat this precaution, with even
less of an explanation as to the dynamics. These sites
can be found in the search results I've provided below.

These sites include:

USHIO.com

"Do not touch the Halogen bulb surface or inside reflectors
 with your bare hands. Oils from skin can lead to breakage
 or shorten the life of the lamp. Use clean gloves or lint
 free cloth for installation and removal."
http://www.ushio.com/safety.htm

TopOneMall.com

"Bulb Care: Do not handle the glass part of a halogen bulb.
 The oil from your hands or any other residue on the glass
 can cause the bulb to burn out prematurely. If you
 accidentally touch the glass clean it immediately with
 isopropyl alcohol and a lint-free cloth."
http://www.toponemall.com/94310wutonmlihgedba.html

Page 10 of this pdf file from Helios, Proteus & Apollo
Lighting Systems:

"Do not touch the new bulb with your fingers; using a
 cloth to hold the bulb, gently push it into the socket.
 If there is any doubt that the bulb may have been
 contaminated by your touch, you should clean the bulb
 before its first use. Take a clean cloth dipped in a
 small amount of rubbing/isopropyl alcohol and gently
 brush off the bulb surface."
http://www.halcyon.net/manuals/helios-proteus_webmanual03.pdf

And, finally, and directly to the point of your question,
from SandCastleDesigns:

"Touching a halogen bulb with your bare hands will ruin it."
http://www.sandcastledesigns.com/tipofmonth.htm


Please do not rate this answer until you are satisfied that
the answer cannot be improved upon by means of a dialog
established through the "Request for Clarification" process.

sublime1-ga


Searches done, via Google:

touch ruin "halogen bulb"
://www.google.com/search?q=touch+ruin+%22halogen+bulb%22

touch oil "halogen bulb"
://www.google.com/search?q=touch+oil+%22halogen+bulb%22

+why not touch "halogen bulb"
://www.google.com/search?q=%2Bwhy+not+touch+%22halogen+bulb%22

Thank you for your wonderful answer.  You provided me with exactly
what I wanted and more.  As you may know, my question was one of the
problems in Google Guide, a tutorial on searching with Google.  You
can find this question at the end of Evaluating What you Find section,
 www.googleguide.com/page_24.html#exercises and part of your answer on
http://www.googleguide.com/page_41.html#halogen.

Nancy...

Thanks for the great rating and the tip.

I also wanted to point out a minor typo on the first link
you mentioned:
www.googleguide.com/page_24.html#exercises

It states the question as:

"Is it true that if you touch a cold halogen bulb with clean
 fingers, will you ruin the bulb?"

'Will' and 'you' should be transposed, so that it reads:

Is it true that if you touch a cold halogen bulb with clean
fingers, you will ruin the bulb?

Best regards,

sublime1-ga

Thanks for pointing out my typo.  I fixed it and hopefully didn't
introduce another.

Nancy

I don't have a source for this, but I had understood that the problem
with halogen bulbs was heat.  Halogen bulbs can get quite hot, and
have started fires when curtains, etc have been near halogen bulbs. 
If the bulb has a smear of oil or anything else on it, that smear will
absorb heat energy and get hotter than the rest of the bulb.  If the
temperature difference is great enough, the thermal stress can break
the bulb.