Thread Tools Display Modes
Old 12-31-2006, 03:03 PM
boytyperanma boytyperanma is online now
Join Date: Dec 2005
Location: Leominster MA
Posts: 5,221
Headlight bulbs why shouldn't I touch them?

When purchasing a new bulb for my 200 chevy malibu I was given instructions not to touch the glass part of the bulb. I thought it was an odd instruction then later in the days while talking to my father he mentioned the same thing. Why is this? is it toxic or something?
Old 12-31-2006, 03:05 PM
tbdi tbdi is offline
Join Date: Nov 2006
Posts: 314
I think the theory is that you'll leave oils on the bulb which will cause the glass to heat unevenly and possibly break.
Old 12-31-2006, 03:06 PM
Common Tater Common Tater is offline
Join Date: Jul 2006
Posts: 1,855
The halogen or similar units get very hot, and the dirt/oil from fingers should cause premature failure.
Old 12-31-2006, 03:07 PM
Q.E.D. Q.E.D. is offline
Charter Member
Join Date: Jan 2003
Location: Richmond, VA
Posts: 22,536
No, it's not toxic, but it can shorten the life of the bulb, sometimes considerably. Your fingers deposit oils and other stuff on the surface in the form of a fingerprint. When this stuff heats up, it can weaken the glass to the point that invisible fractures form, allowing air in and the bulb fails. Sometimes, they can even shatter although this is more likely to occur in higher-wattage bulbs such as used in TV studio lighting.
Old 12-31-2006, 03:10 PM
Don't fight the hypothetical Don't fight the hypothetical is offline
Join Date: May 2006
Location: NoCal
Posts: 1,696
Seller of Task lighting here. I have seen first-hand new bulbs shatter from having been touched. It's the oils from your skin as noted above.
Old 12-31-2006, 03:37 PM
Q.E.D. Q.E.D. is offline
Charter Member
Join Date: Jan 2003
Location: Richmond, VA
Posts: 22,536
If you do touch it, all is not lost. Use a soft towel or rag soaked in a solvent like plain rubbing alcohol or acetone to wipe down the bulb before you've turned it on and wipe it dry. I imagine window cleaner would do well, too, since it does a fine job with fingerprints on windows. Best thing is to handle it while wearing clean, oil-free cotton gloves to begin with.
Old 12-31-2006, 09:06 PM
HMS Irruncible HMS Irruncible is offline
Join Date: Nov 2004
Posts: 7,170
We did this one to death, gosh, seems like a year ago:

Pay particular attention to the excellent summation by yours truly:
Old 12-31-2006, 09:35 PM
Rick Rick is offline
Charter Member
Join Date: Aug 1999
Posts: 16,451
Also from that same thread, a do it yourself experiment for the doubters out there.
Old 01-01-2007, 07:21 AM
ticker ticker is offline
Join Date: Apr 2000
Location: London
Posts: 1,958
Missing from all the above explanations is that salts from your skin also have a deleterious effect on quartz glass. Quartz (i.e. pure SiO2) glass is used because it has very low thermal expansion and so can withstand greater thermal shock than regular soda glass, which contains sodium to make it easier to work in the molten state. Sodium ions from your fingers will affect the expansion properties locally, leading to rapid failure.
Old 01-01-2007, 12:38 PM
Chefguy Chefguy is online now
Charter Member
Join Date: Jun 2003
Location: Portlandia
Posts: 39,082
Disregard all pseudo-scientific nonsense. The bulb are phobic and don't like to be touched. It gives them issues, causing them to crack up.
Old 01-01-2007, 01:05 PM
Rick Rick is offline
Charter Member
Join Date: Aug 1999
Posts: 16,451

Why didn't I think of that!
So what you are saying is these bulbs are kind of lighting equivalent of Adrian Monk, and have issues.
Perfect. Got it.

Chefguy it is official, you gave me my first laugh of 2007. Thanks.


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 10:12 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

Send questions for Cecil Adams to:

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to:

Copyright 2018 STM Reader, LLC.

Copyright © 2017