RE: [ATM] quality suffering

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

Last Friday one of the mirrors being figured in our
class had the most amazing little flaw near one edge.
With the naked eye you could see a little groove about
3 or 4 mm long and maybe 0.2 mm wide, and it also
appeared to have 6 'legs' coming out of it, sort of
like water-strider insects on a pond. The flaw was
very clearly visible in the Ronchi/Foucault tester,
also, as a fairly large and obviously wrongly-figured
area of the lap (say, about a 2 cm diameter area). We
were wondering if a flaw in the blank had suddenly
worked its way up to the surface; but that is not very
likely, since he is merely figuring at this stage.
None of us had noticed anything like this before hand.
The blank comes from United Lens. Sorry, I forgot to
look at the deformity with a magnifying lens. There
are no bubbles anywhere in the mirror blank that I can
recall.

A few possibilities occur to me:

(1) it really is the fossilized imprint of a water
strider, which was, most likely, out for a leisurely
water-stride on the vat of molten borosilicate
mixture, and fell in, and this person merely uncovered
its remains on Friday evening.

(2) The deformity it had been there all along [for
whatever reason] and we just didn't notice it until
Friday. (sort of like #1)

(3) the Pyrex in that part of the blank is stressed,
possibly because of poor mixing and annealing, and the
grinding and polishing and figuring process all of a
'sudden' released the stress in that area and caused
the deformity we saw.

(4) Somehow a large piece of rough grit fell on his
lap and made an insect-body type of outline just in
one small corner of the lap, without any scratches
being evident anywhere -- AND the deformities in that
area do not appear to be scratches to the naked eye. 

(5) We eat crabs and shrimps, which IS an abomination
unto the Lord, and he is wreaking His vengeance upon
us. (Plus, I 'knew' my wife before we were lawfully
wedded, which is another abomination.)

(6) It's a bubble that we never saw until now.

Any thoughts?

Guy Brandenburg
--- Richard Schwartz <richas@earthlink.net> wrote:

> I will agree with this wholeheartedly that quality
> and availability of ATM
> supplies is declining.  


=====
Guy  BrandenburgWashington, DChttp://home.earthlink.net/~gfbranden/GFB_Home_Page.html

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