Ed Huntress wrote:
"axolotl" wrote in message
...

Ed Huntress wrote:
But glass, and other

glassy materials, can form crystals under specific conditions.

Inquiring minds and all-

How does one make a glass crystal without introducing impurities (and
making it simply glass like)?


Kevin Gallimore


'Can't help there, Kevin. Quartz is, of course, chemically identical to
glass, but is crystalline. And practically all glasses contain impurities.

That's a bit like someone I saw calling inconel stainless steel. While
common glasses are predominately SiO2 it does have significant additions
of other chemicals to give it the required properties and to lower the
working temperature to something acceptable. Citing wiki
http://en.wikipedia.org/wiki/Glass for some info, although I think it is
wrong with the melting point for SiO2 which is normally given as 1650C.
I do some glassblowing as a hobby and the glass is normally gathered at
about 1050C(1922F) to 1100C(2012F) depending on the glass type, the lead
glass being 24% PbO, by weight I think. The glass used for manual
glassblowing being formulated to give a long working period, whereas
machine made glass typically stiffens much more quickly to suit rapid
turnaround. A very different material to quartz.

--
Ed Huntress