Re: [ATM] How to test a mirror blank?

[Jarvis Krumbein <jkoptic@juno.com>]

Aaron, I don't think you will have any problems at all with that piece of
glass.  I'd go for it.

Jarvis
 
On Wed, 04 Oct 2006 23:47:56 -0700 Aaron L Taylor
<lists@subgeniuskitty.com> writes:
> For reference, the polarizers in the set of photos are 8.5"x11" in 
> size.
> 
> I tried the idea suggested by Jarvis and Tom of using an LCD screen 
> as 
> the backlight for the mirror. This time, there was no evidence of 
> the 
> strong stress that the previous test showed. Instead there was one 
> stress arc that seems very mild. I was also able to see every piece 
> of 
> dust on my LCD. :-)
> 
> I was pretty sure that what I saw in the first test was stress in 
> the 
> mirror. Previously, when I had rotated the mirror, the lines had 
> rotated 
> with it. In order to verify this, I duplicated the test and saw the 
> 
> lines. I then rotated the mirror and the lines did not rotate. The 
> only 
> thing I had changed was the first polarizer. Originally I had taped 
> it 
> to the mirror as I was rapidly running out of hands to test with. 
> This 
> time I had my girlfriend holding the polarizer in place when the 
> mirror 
> was rotated.
> 
> It turns out that the horrid stress marks I saw originally were from 
> the 
> protective sheet on the polarizer. After removing a thin plastic 
> sheet 
> from the polarizers surface, the lines went away and I saw the same 
> 
> image as when I used the LCD.
> 
> Here are the updated images:
> 
>
http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_str
ain/mirror_strain_lcd_01.jpg
>
http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_str
ain/mirror_strain_lcd_02.jpg
> 
> The mirror is rotated 180 degrees between the two images.
> 
> Does that level of strain in the glass look acceptable?
> 
> Thanks,
>    -Aaron Taylor
> 
> 
> 
> Jarvis Krumbein wrote:
> > It's hard to tell from your pictures as to what you've got there.  
> How
> > big are your polarizers?  If you have a lap top or an LCD display 
> for
> > your computer, use that with a blank white screen for your light 
> source. 
> > It's already polarized and you can see the whole mirror at one 
> time. 
> > This will give you a much better idea of the strains.
> >
> > Jarvis
> >   
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 
> 
 
_______________________________________________
ATM mailing list http://www.atmlist.net/