[ATM] Working with plate glass - the figure changes like theweather

[toolontop at yahoo.com (Mark Cowan)]

--- Guy Brandenburg <gfbrandenburg@yahoo.com> wrote:
> One of the folks in our mirror-making class has been
> struggling - and I do mean that literally - with a
> small (4.25", f/9.6) mirror that he got from Newport
> Glass. ...> 
> He and I will spend time figuring it, and we will
> think it is just about perfect when we look at it
> ... Then we look at it the next week -
> and
> it's totally different. 


You might want to check the anneal.  If it was
actually supposed to be a tool it'll show an
impressive Maltese cross pattern under crossed
polarizers - and it'll /never/ work as a mirror.

If it is annealed properly, you should be able to work
it, let it cool, test it, and test it again the next
day with no change.  If all else fails apply the fire
hydrant test for proper annealing.

Cheers,
Mark Cowan
Salem, OR USA


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