Re: [ATM] FW: Figuring flats

["Philip Lardner" <philiplardner@eircom.net>]

I have observed that touching (even momentarily) the crack between the two
plates under test (to check they are centred) produces a very noticeable
local bulge / distortion in the fringe pattern requiring another 30 minutes
or more to dissipate. To date I have worked the three plates tool-on-top. My
tool is a good 2" thick concrete on floor tiles. I never touch the plate
itself after I start pressing it - except briefly to rotate it mid-session,
and then only the back edge.

Phil.

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net]On Behalf Of
Vladimir Galogaza
Sent: 12 March 2007 21:03
To: ATM List
Subject: Re: [ATM] FW: Figuring flats

Mike,

>Do you worry about the deformation breaking the glass?

No, I worry that  fast heating of one side will cause bulging
and polishing will remove part of the bulge. When cooled there will be
depression.

Dale demonstrated that short touching with finger of the mirror
surface results in detectable glass bulge.

Regards
Vladimir



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