Re: Exciting news regarding halogen bulbs!

[bercov@xxxxxxxxxxx (John Bercovitz)]

> Out of curiousity, what is the practical difference between a halogen bulb
> and a Krypton bulb? Or how do they compare? (brightness, colour, life etc).

Well, I'm not an expert but maybe by spreading lies I can scare an expert 
like BobH out of the woodwork.  8-)  A krypton lamp has a gas-filled bulb  
and in this case the gas is primarily krypton.  The gas allows the filament 
to run at higher temp without burning out so fast.  I'm a little unclear on 
this but I think it's because then oxygen can't so easily get to the filament 
Any of the ordinary higher color temp lamps are gas filled and I don't know 
what the special advantage of krypton is other than it sounds like something 
from Superman's home planet.

A halogen-cycle lamp uses a halogen such as iodine to return evaporating 
tungsten to the filament.  This means the tungsten doesn't deposit on the bulb 
walls, reducing light output significantly long before the filament is a goner.  
The walls of a halogen-cycle lamp have to run hot to keep the iodine/tungsten 
from depositing on the walls.  So be careful - too hot to touch.  Many halogens 
use quartz for an envelope material and then you have to be careful careful 
about fingerprints because quartz+fingerprints+heat gives severe degradation 
of the quartz.  So install quartz halogens with white gloves.  I think ethanol 
may be the right thing to remove accidental fingerprints but I could be dead 
wrong on that.  I don't think the iodine returns the tungsten to the filament 
evenly, much like when stuff hits the fan it never gets distributed evenly, at 
least around this lab.  So I don't know if it helps much with notching, the  
bane of a filament's existence.

John B


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