Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Tom Phillips wrote:
> I guess one key piece of information would be what is the
> shortest bulb life that a real PI has had a bulb explode at.  The 
> important fact is not how long they can possibly last but the minimum 
> time before a properly handled one explodes. 

--This may not be as useful as it sounds, since there are lots of 
incidental things that can happen to bulbs that increase their 
likelihood of blowing: dropping them, handling them with bare fingers 
(--> oil carbonizes, producing a focus of heat buildup), etc.

Operator error is also a consideration.  I think I've blown 3 or 4 bulbs 
in my career.  Two or three were in an old Zeiss pumpkin lamphouse that 
took the 200 watt bulbs.  In one of those cases, we had turned the 
lamphouse sideways to save space in a tight location.  It was a great 
idea except that the lamp was cooled by convection and the heat now had 
to try to find its way out the side rather than flowing smoothly out the 
top.  Oops.  In another case, I had a new OptiQuip lamphouse that 
accepted 200 W Hg lamps.  We had a bunch of the old 200W lamps from the 
Zeiss around so one day I stuck one of those in--it fit, it was 200W, so 
why not, eh?  Unfortunately, the OptiQuip was designed for 200W DC lamps 
and the Zeiss took a 200W AC lamp.  Ka-blooey!

> Other useful information 
> would be an assessment of the hazard of the mercury vapor that escapes.  
> Finally, I have heard of lamp housings being damaged by the explosion. 
> Is this really a likely scenario?

Hard to know about the real danger of the mercury but the stuff has a 
relatively low vapor pressure for a metal.  I would evacuate the room, 
shut the door immediately (preferably without breathing in) and let the 
HazMat team decide the danger.  --In any case, on each occasion when a 
lamp has blown, it has cost me the collector lens and the reflector 
mirror (if the lamphouse had a mirror).

I now try to limit my experiments with pyrotechnics to outside the lab.

Martin Wessendorf
-- 
Martin Wessendorf, Ph.D.                   office: (612) 626-0145
Assoc Prof, Dept Neuroscience                 lab: (612) 624-2991
University of Minnesota             Preferred FAX: (612) 624-8118
6-145 Jackson Hall, 321 Church St. SE    Dept Fax: (612) 626-5009
Minneapolis, MN  55455                E-mail: [log in to unmask]