Re: [ATM] Microwave heating of glass

[Dominic-Luc Webb <dlwebb@canit.se>]

Several things to point out here, as this is potentially usefeul
for making mirrors.

1. A form would be needed, either for the shapre of the mirror
or as a crucible. We would need to think on appropriate
material for a microwave.

2. There are a few quite cheap ways to get the temperature needed
to get this process started. There are a number of heating elements
that could reach this temperature (600-800 C ???).

3. Getting broken glass melted enought to mix and fuse properly
without a lot of bubbles and stress is a whole separate issue. I
have accomplished the same thing that microwave video did by just
burying a lot of glass into a pit in my garden and burning a
fire around it. There are no practical size limitations, so massive
mirrors are possible. However, when starting with a lot of
broken glass, the pieces first become kind of high viscosity liquid,
much like syrup, but the different pieces won't truly mix, although
they might fuse as the system cools. I think a much higher
temperature must be needed for mixing, and it is not clear if a
microwave is up to this task, especially since we would be most
interested in melting sufficient glass to make larger mirrors.
Smaller mirrors of the size that would fit into a typical microwave
can be made with plate glass, which questions the useful of the
microwave, unless it can be scaled up to a larger size. Indeed,
I have considered applying this classical physics demonstration
by combining the microwave elements to a larger chamber. I never
got far with this partly because it was clear that when I am
ready for the larger mirror, the pit in my garden will likely
just work. Since the fire pit is buried, it has a cheap and
convenient means for slow annealing....

4. A proper way to anneal would be needed. Since the energy
level is readily controlled on any microwave, this might be
doable through use of progressively lower settings over time.
I am actually concerned about the non-uniformity of the energy
within a microwave. I suspect there would be a lot of hot and
cold spots. This would need to be made more homogeneous.


Dominic Webb

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