Re: [ATM] mirrors

[Bill Marriott <bmarriott@pacbell.net>]

Richard;

Probably a year ago or so, I did indeed polish flat both sides of an ASM 
8" blank, when held up to the light, you can see inconsistantcies in the 
'color' distribution of the black, with areas of green 'Pilkington 
technical glass" color showing through here and there.

I then brought it to the Chabot Mirror making lab, and with Richard O, 
set up a light and a pair of polarizing filters, the glass was 
illuminated just fine,  and we were supprised to see the glass darken 
evenly, with no sign of stress or straie.

That was just one piece of glass, btw. Who knows what lurks in other, 
bigger, ASM blanks.

Regards

Bill Marriott
VA Optical Labs





Richard Ozer wrote:

> Oh yes... one more thing.
> 
> Considering the lengthy thread on annealing this week and the importance 
> of testing for stress; one thing that is difficult (nearly impossible) 
> to do with the ASM product is test it for stress... it's black and cross 
> polarizers are a useless with an opaque material.
> 
> However, I remember Bill Marriott was able to flash polish both sides of 
> a piece of BVC and I seem to recall him getting light to pass through 
> it.... I may have imagined this; maybe he'll chime in....
> 
> RO
> 
> Cec & Cris wrote:
> 
>> Hi everyone
>>
>> My name is Cristian and I have just joined your group.
>> I'm in the process of grinding out a 250mm mirror(I'm up to the fine 
>> grinding stage) and I'm already looking into my next project. In 
>> Australia it's difficult to find mirror blanks, most come from 
>> overseas and cost a small fortune. Through your links I came across 
>> ASM products page and I was wondering if anybody out there had made 
>> mirrors using their products and if they hold their shape due to 
>> temperature changes. I want to make a 24 inch mirror.
>>
>> regards Cristian
>> _______________________________________________
>> ATM mailing list http://www.atmlist.net/
>>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 

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