Re: ATM 10mm thick float glass

[Michael Coslo <mjc5@psu.edu>]

At 12:07 AM -0700 7/16/99, Paul Forshaw wrote:

        First, plate glass is soda-lime glass, so you need to be sure what
the other glass is. Float glass can be most any type of glass, but check to
be sure what type it is. The most important thing is that it is not
tempered glass. If not tempered, it will work.

>1) am I deluding myself that such a thin chunk of glass could be turned into
>a decent mirror ?

        No, you are not. An inch thick, 9 inch blank is a little thin, but
will work well if you support it well during grinding and polishing. You'll
also need a good cell design, but you should have a good cell design
anyway. 8^)

>2) for a first-time glass pusher, would I be better off paying up the $50
>for a standard thickness plate glass blank ?

        I would go for the less expensive glass.


>3) is float glass really that bad - just the mention of it on s.a.a elicits
>sour faces (or their electronic equivalent) :-)

        The mention of anything on s.a.a does that, doesn't it?  ;^) Just
ask what the best color for a scope tube is, or if Jean-Luc Picard can beat
up Captain Kirk.


        But seriously, soda-lime glass does have some characteristics that
are different than pyrex glass. It expands more quickly when the
temperature changes, so when you figure it, you have to do shorter figuring
sessions, and allow the mirror to rest several hours before testing ( a
long wait is not all that bad an idea even with pyrex)

        It will make a good mirror.

        - Mike -