How To Clean Halogen Bulb After Touching

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Touching halogen bulbs

Discussion in 'Lighting' started by Andy, Apr 27, 2006.

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Is it too late to clean a quartz bulb if I have touched it during
installation?
I will have already deposited skin oils and grease.
Andy wrote... You can clean the envelope using alcohol - surgical spirit or iso-propyl
alcohol, as available. Then don't touch it again!
David
No. Just clean the bulb surface.
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I'm thinking at most a slightly shortened life span of the lamp.
Assuming the lamp is a general lighting lamp -- no big deal. Clean it
(alcohol or window cleaner will do), wipe it dry with a tissue or clean
cloth and turn it on.
Or, just forget it unless there is some sophistocated optical system
involved. The worst that can happen is that the surface of the quartz will
diffuse slightly. Lamp life will not be affected.

Terry McGowan
wrote... You would probably need to apply the grease with a butter knife! In my
experience contamination tends to lead to de-vitrification of the quartz
envelope and early failure but I've never had one burst. I always believed
that it was the salts from your fingerprints that did the real damage -
diffusing into the silica - but of course you need to dissolve the finger
grease with alcohol before you can wipe off all the salts.
David
The early failure and/or rupture of halogen lamps contaminated by finger
prints or grease are widely-held notions; but in several decades of product
service experience with a major lamp manufacturer and the inventors of the
halogen lamp, I've never seen any evidence of such a problem with general
service halogen lamps. Sure, dirt can cause some fogging (devitrification)
of the quartz surface; but that's a long ways from bulb softening and
failure.
I'd be interested in hearing from anyone who (really) has had or seen such
problems -- again emphasizing for general service lighting lamps, not
stage/studio, reprographic or other special purpose halogen lamps that are
designed closer to the limits of the materials.

Terry McGowan
Stage/studio lamps are certainly more likely to have problems such as you
describe. For one thing, the filaments are operated at higher
temperatures -- 3200K vs. 3000K, for example.
It's normal for the quartz envelope to glow after switch off; but not to
bulge. That says the temperature of the quartz is at the softening point.
Not good.

I wonder if the reflector was refocusing the energy back onto the lamp in
that particular case. Sometimes when a spherical reflector section is used,
that happens.

Terry McGowan
I've had one fail after a 1 meter fall while on (220 volt tube).
It kept working and I placed it back. I thought: hmm, these are fairly
string. About 30 seconds later it went, I believe taking the house fuse
with it. It had spewn out its filament over quite a distance.

Please keep the fittings grounded/earthed.

Thomas

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