Re: [ATM] Ultrathin Project update

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

On Wed, 16 May 2007, Richard wrote:

> something infinitely rigid that conformed exactly to the convex surface
> then there wouldn't be a problem, agreed?
>
> How can we approach that?. The one thing that came to mind was setting
> the convex side in fine plaster in such a way that there is no stress

Well OK, I have actually been doing this by several approaches. They
are all problematic. In one attempt, I put the glass into concrete.
A bit of grinding quickly removes any concrete on the surface. I
have used other substrates as well. The problem here is (I believe)
the variable swelling of these materials with temperature and
moisture. Such thin glass will simply conform to the shape of the
underlying substrate. Virtually any support other than actual glass
will have more problems with deformation from temperature and
moisture. At some point, you start questioning the point of this
exercise.

And so, I tried emulating Richard Schwartz' thermal diffused mirrors
by adding cut pieces of glass and supporting with that.... much,
much better. Take a look at this:

http://www.canit.se/~dlwebb/catadioptric/320tdb/slump_fused_primary2.jpg

Now imagine a concrete form that is not rigidly connected to any of this
glass, but just provides a frame to hold the smaller underlying glass
pieces upright. For me, the ultralight is a fun experiment, but I
think Richard's thermal difussion is better overall since the glass
pieces are actually integrated into the mirror, giving the mirror
rigidity of thicker glass. I note that the present mirror was
slumped, so since there is a kiln available, maybe it is worthwhile
to have a go at thermal difussion bonding.

Dominic-Luc Webb

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