From: "Russell Jocoy" 
To: bcjawsss24{at}verizon.net, atm{at}shore.net
Reply-To: "Russell Jocoy" 


>From: "Arthur" 
>Reply-To: "Arthur" 
>To: "atm{at}shore.net" 
>Subject: Fw: Re: ATM Port hole glass
>Date: Wed, 2 Jul 2003 15:58:17 -0400 (Eastern Daylight Time)
>
>
>
>
>-------Original Message-------
>
>From: Arthur
>Date: Wednesday, July 02, 2003 03:07:40 PM
>To: bobmay{at}nethere.com
>Subject: Re: ATM Port hole glass
>
>
>Bob,
>
>I have a Polaroid draw shade that I have cut down to size, I've read
>everyone's replies and did my search in the archives. However, I'm not
>clear
>as to how exactly this test is done. For starts, we haven't had a clear day
>here in a month, so a clear day for reflected sun light isn't readily
>available (in Florida??). I read somewhere to use a Polaroid film with a
>back light, and another in front to check for stress. I put the film on one
>side of the glass with dim light just behind it, then took a second sheet
>and held it in front. I moved the second sheet around in all directions. I
>didn't observe any changes. How far a part should the film be on both
>sides?
>can I use a flash light as a light source? I'm just not getting it...
>
>
>Bill
>
>-------Original Message-------
>
>From: Bob May
>Date: Tuesday, July 01, 2003 02:42:28 PM
>To: atmlist
>Subject: Re: ATM Port hole glass
>
>If you have some polaroid sunglasses (the ones that claim to reduce the
>glare over water, etc. and are gray colored) you can do the test for stress
>in glass.
>Start by finding a nice glancing reflection of the sunlight off of a car or
>other window. This glancing reflection polarizes the light and the more of
>a glancing reflection, the stronger the polarization. This is the fist
>polarizer on the test.
>Next, hold the piece of glass up to the reflection and look at it wearing
>the sunglasses, either on the face or holding with the other hand so you
>can
>rotate them. This is the glass under test rotating the polarization with
>the stress in the glass and finally the detection of that polarization
>change with the polaroid sunglasses.
>A good piece of glass will have an even color and when you do the
>extinction
>of the light by crossing the polarizers, the whole glass will evenly fade
>in
>brightness. A piece of glass that has stress in it from tempering will have
>spots and/or lines in the brightness and will be basically unusable as it
>will shatter at some point rather than allow for the grinding of the
>surface.
>FWIW, I've gotten some that have indications of temper but were in fact not
>actually tempered and all have been ground well and work fine. All of the
>pieces had no stress when doing this test.
>Bob May
>http://nav.to/bobmay
>bobmay{at}nethere.com
>NEW! http://bobmay.astronomy.net
>
>
>
>.
>
("atm{at}shore.net")


Arthur,

       You have done the test correctly if you had one  poliorized lens at
your eye, and the other at the other side of the glass.,, as long as you
rotated the two opposite directions to the point of almost black and moved
both across the surface and found no "FOG" or Shadows, you can
grind to your hearts content...
                                 Russ
("atm{at}shore.net")

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