> William Couture wrote:
> 
> > I suggest an experiment:
> >    1) A piece of metal with a hole in it
> >    2) A THIN-WALLED glass "jar" the exact size of the hole 
> in the metal
> >        (a light bulb will do)
> >    3) Appropriate heat source.
> > 
> > Put glass "jar" in hole.  Apply heat.
> > 
> > See if "jar" breaks.   If it does, the hole has shrunk.
> > 
> > If it falls out, the hole has expanded.
> > 
> > Let me know how this turns out.
> 
> I might do that if/when I have the required equipment. OTOH, 
> the expansion coefficient of glass (9 ppm/K) is close to the 
> one of iron/steel (12 ppm/K), so this is probably not the 
> best "hole filler". Quartz (<1 ppm/K) is probably better (but 
> more difficult to find around the house).


Pyrex has COTE of about 3.

Glass fusers are very concerned in the expansion properties of glass.  Glass
is 8.5 to 10 (mostly 9), if you fused two pieces together and the difference
between the expansions rates is even 0.1 apart, the glass will crack.

Interesting picture at the bottom of this page -
http://www.warmglass.com/Compatibility_testing.htm.  Under polarised light,
the incompatability shows up.

(Glass people move the decimal point, so 9 is 90).

Tony

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