Re: [ATM] practical limits of 1 inch mirror

[David Weinshenker <daze39@earthlink.net>]

Olivier Biot wrote:
> I know of at least three 20" mirrors currently under construction (one
> still rough grinding, the other 2 already in polishing) that were made
> from 25mm borofloat. The tool was made from two (much cheaper) 18-19mm
> float glass disks glued together with a bonding agent based on RTV
> (silicone).

> Regarding annealing, it appears that we have access to very high
> quality float and borofloat glass over here, nearly making a polarizer
> obsolete. We don't need to anneal our blanks for quite some time now.

So Borofloat is well-annealed as supplied in sheet form?
That's good to know... now I just need to research US
suppliers (either of raw sheet or edged round blanks) -
I don't know if the Schott North America office themselves
will deal in small "end use" quantities or only in bulk
orders...)

It's starting to sound like 25mm Borofloat might
work very well indeed for a 10-12 inch mirror,
from what I've been reading here.

-dave w
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