Re: ATM Has anyone worked with membrane mirrors?

[astillma@nit.AirTouch.COM (Anthony Stillman)]

Dr. Hennecke wrote:

I wonder if this could be used in reverse: instead of a vaccuum below
the membrane apply pressure on top. For example, by stretching ceran
wrap over a pot and pouring plaster on top could one make a curved
tool?
...
Maybe use some kind of ring to stretch the foil over and
measure the sagitta from below while slowly pouring the plaster on the
foil?
...
The advantage of using a membrane to make a tool instead of a mirror
is that not nearly the same accuracy is required.
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GUNIUS!

I wish I had thought of that.

Plaster does change weight when curing, but not much before it hardens.
Further, it expands as it hardens.  Also, other casting materials don't
change weight much at all.  Stucko, for instance.

This definitly goes into the list of good ideas.

Anthony