ATM ? Test for Strain in Coated Mirror

["Jan and Rod Shea" <jnrshea@comcast.net>]

Hello All,

Does anyone out there know a way to test for strain or annealing problems in
a coated mirror?  Can you shine polarized light at the back of the mirror
and look at the reflection off the back of the coating through a polarizing
filter?  Would this double pass through the glass change what I would see?
I am also having a little bit of trouble rigging a 1.25" polarizer onto a
flashlight and getting a beam wide, bright, and even enough for this 24"
mirror.  Seems like I could get a large polarized screen, or try a
reflection from a large, flat, second surface mirror once the sun comes out,
but has anyone else come up with a simpler way?

Thanks,

Rod