Re: Smiley Faces!

[Doug Craigen <dcc@cyberspc.mb.ca>]

David Dockstader wrote:
> On Wed, 23 Sep 1998 10:00:44 -0400 Chuck Britton said:
> >       So now we know that Quartz-Halogen bulbs are CRYSTALLINE!!!!
>
> or maybe that they don't contain quartz?
> We had a good discussion about the halogen part a while back and I think we got
>  that part straight.  Anybody know where the quartz part of the name comes from
> Is it because the hotter bulbs require a higher melting glass and somebody
> decided to call it quartz?
>
> Quartz is a mineral name, and like all minerals has a definite crystaline
> structure.  Melt the quartz and then cool it quickly so there is no long
> range crystaline structue and you have glass.  This is the definition of the

Back to my "semantic minefield" comment of a few hours ago. Check out
http://www.heraeus.de/e/quartz.htm where a company that makes and sells
quartz makes the following statement:
             Quartz Glass
             Heraeus Quarzglas is a technological and market leader in
the
             production and processing of high-purity quartz glass. A
number of
             unusual optical, mechanical and thermal properties have
made
             quartz glass an indispensable material in the fabrication
of
             high-tech products. 
or perhaps, check out the welding of quartz glass at
http://www.ping.at/ptg/quartz.htm
or another quartz glass seller at http://www.culimeta.de/indexquarz.htm

.... and so on and so on.  Put "quartz glass" into your favorite search
engine and see how common the term really is.

*****

My guess is that there are factions of minerologists and/or materials
scientists who find this as offensive as we would "weight in kilograms",
but there it is - common useage of the term.

***

My guess would be that these bulbs genuinely use SiO2 rather than a high
temperature glass such as a borosilicate.  It has to lowest coefficient
of thermal expansion and therefore the least chance of breaking due to
stresses from thermal gradients (which must be considerable for these
bulbs).  The withstanding of stresses from temperature gradients or from
mismatching of coefficients of thermal expansion with other materials
used in high temperature regions of a device a device are more important
than the melting point in the failure of glass devices at high
temperatures.

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Doug Craigen          "Technology with purpose"
                       http://www.dctech.com