From: SFPhysics@aol.com
Date: Sat Mar 29 2003 - 14:33:36 PST
From: SFPhysics@aol.com Message-ID: <90.34beb5b6.2bb77940@aol.com> Date: Sat, 29 Mar 2003 17:33:36 EST Subject: Skin Oils damaging Halogen Lamps
I replaced a halogen bulb recently and read the
warning not to touch the bulb. I understand that it
significantly decreases its life. Is this because the
high temperatures change the permeability of
glass?Curious.
-Jon Cohen
Greetings Jon:
Those halogen lamps are made of fused quartz because they have to operate at
a much higher temperature than most types of glass would allow. The halogen
lamps also put out a lot of ultraviolet radiation, and along with the heat,
the oils in the fingerprint then carbonize. Thus the surface of the print
will then turn dark and draw extra heat. Very likely that concentration of
extra heat will melt the fused quartz at that spot or at least cause extra
expansion which will crack the bulb and lead to instant failure. The globe
shaped halogen overhead projector bulbs were the most susceptible and any
skin oil usually led to a quick "pop" failure.
Some glow discharge spectrum tubes used in Physics demos will sometimes
carbonize fingerprints in a like manner so these should be cleaned and
handled in such a way as to minimize fingerprint oil buildup.
Best wishes,
Al Sefl
Who single-handedly supported most school fundraisers involving chocolate...
And who left chocolate fingerprints everywhere except on halogen bulbs...
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