Re: ATM Does gluing two blanks together work?

[Dennis Rech <dennisrech@home.com>]

Several years ago, one of the elder ATM tinkerers in our club left me a number
of 12 and 16 inch portholes that had been epoxied togeter. Each half was 3/4
inch thick. Checking stress with polarized light revelled a large blue
cross in
the center of each piece plus indications of other stresses. I slowly warmed
one of these glued blanks in the oven until the exopy started to stink and was
able to lever the two sides apart. Each tested much better than the
combination
(but each still showed a little stress).
When two pieces of glass are glued together, there is a thermal break which
can
cause a bi-metalic effect when one side is at a slightly different temperature
than the other. 
Heat fused blanks can work well, but glued blanks will have problems.
Dennis
Dennis Rech
Mirror-o-Matic

http://www.oblivion.net/~astro/mirror/