OT: nifty equipment sighting

dwight elvey dkelvey at hotmail.com
Sat Sep 29 22:50:58 CDT 2007

> Date: Sat, 29 Sep 2007 18:43:15 -0600> From: bfranchuk at jetnet.ab.ca> To: > Subject: Re: OT: nifty equipment sighting> > Dave McGuire wrote:> > > I'm no chemist, but I assume they're some oxide of tungsten. That's > > what happens when an incandescent light bulb blows out due to loss of > > vacuum. Pretty amazing stuff, if you ask me.> > Looks organic like some thing was realy growing.
 This doesn't look like oxide, it looks like tungsten crystals.
these form as the filament evaporates and recondenses on
the filament. This is part of why they fail. There are two
factors. One is that they tend to thin over time by
evaporation. The other is that they tend to get more brittle
over time.
 It is rare to see one fail because of loss of vacuum but
when it does, the filament turns to a whitish yellow powder.
 Most lights do not have a high vacuum. If they did, the
glass would cover with evaporated tungsten quickly
and bock the light. You might notice that only the tops of the
bulb get darkened. This is because of simple convection of
the gas in the bulb.
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