From: "Andreas Derwahl" 
To: "Atm-US \(E-mail\)" 
Reply-To: "Andreas Derwahl" 


> So presumably the alkali-silicate acts to reform the exposed
> glass surfaces
> into a single piece of glass?  Are there any examples of
> this?  I scanned
> through a few webpages of theses and abstracts about alkali
> silicate but
> didn't find anything concrete (bad pun since apparently
> alkali silicate and
> concrete have a history ) about how to go about this, or
> if there are any
> commercial instances of this in the form of aquarium glue.
>
> Mel Bartels


You got me there...
I just took a shot hoping someone with more knowledge in the field would
pick it up...

The only source I found was my old Inorganic Chemistry book
(Holleman/Wiberg), which states that a water-glass solution can be used as
an inorganic glue for broken glass and porcellain. The strongly alkaline
solutions contain hydrogen silicate ions (i.e. H2SiO4 2-, H3SiO4 - etc.)
which are prone to polycondensation, they react with each other and release
a water molecule to form Si-O-Si bonds.

Wether this is used in the process mentioned I don't know. If it is, it
seems unlikely to me that a ribbed mirror made this way would stand up to
the mechanical and thermal stress of grinding and polishing. Whereas
technically the product of the polycondesation is SiO2, it will presumably
be in an amourphous and porous form, so not very strong.

But who knows, maybe it would work? As I said, I could also be completely
wrong and the process has got nothing to do with it.

Andreas

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