Re: [ATM] A very rough surface mirror

["Richard Schwartz" <richard1941@gmail.com>]

I just remembered an incident from 35 years ago.  Alan McIntosh was making
three flats of cer-vit by the A-B-C method, and kept digging out the center
of one of them, no matter the stroke.  It turned out that there was a soft
region in the material itself because of poor mixing during manufacture.

Otherwise, my best guess is that the surface was intended for a non-critical
application where optical quality was not needed.  Perhaps it was polished
with pads at high speed, never tested, never touched by hand, and never put
into contact with pitch.

Our methods tend to be self-correcting so that even the least experienced of
us can do a better job than this.   Obviously our methods were not used on
this piece.

Richard
"California has four seasons: earthquake, race riot, flood, and firestorm."
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