To: ,"Bob Mazzullo" ,
        
From: Mark Suchting 
Reply-To: Mark Suchting 



The fact is that `fine annealed' is a rather `blurry' standard. I continue
to see a mild spread of anneal quality with any glass vendor I deal with.
Most people don't test glass for strain so strict quality control it is not
really a big issue for vendors. If someone complains they'll give you
another piece.

Most Soda- lime glass I look at is very well annealed. Its higher
coefficient of expansion mean that it has to be annealed more thoughtfully,
lest it crack during cooling. Most of the anneal horror stories I've looked
at are in Borosilicate glass .   Soda-lime, when correctly polished, well
mounted and ventilated is capable of just as good performance as
Borosilicate IMHO.  Thickness of the glass pointing to cooling issues is a
much greater issue in performance than that of the mirror material (
experimental  products like BVC not included there ).

~Mark Suchting




At 04:14 PM 8/8/2003 -0700, lenses{at}adelphia.net wrote:
>Let me stop you and others right here.
>We and anyone else can with patience take fine annealed pyrex to much
>better than 1/4 wave.
>We take plate glass to this level of flatness.
>My 2 cents.
>Pete

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