[ATM] Re: 40" mirror more on Pyrex

["Mike Conran" <mike@guidesys.com>]

Jerry, a little more on Pyrex.  Guess it is good to gather all you can about 
what you might be attemping to slump, cast and anneal.

Mike Conron 

 From site: 

http://www.megspace.com/science/sfe/i_fa_cir.html#cooking 

 

 

"7740 pyrex: 

Working Point: 10E4 poises - Glass is a thick fluid, like honey. Only the 
large bubbles will rise to the surface; but small bubbles are trapped in the 
glass. 1252 degC. 

Softening Point: 10E7.6 poises - Glass flows slowly; any structures collapse 
into a horizontal pile. This is hotter than you need for slumping and fusion 
welding. 821 degC. 

Anneal Point: 10E13 poises - Glass is solid, but internal strain is relieved 
in 15 minutes. This is not hot enough for slumping and fusion welding in a 
reasonable time. 560 degC 

Strain Point: 10E14 poises - Internal strain is relieved in 4 hours. 510 
degC " 


Jerry B. Hillman writes: 

> Hi Matt,
> I am looking into Cas, coude, etc. designs, but haven't learned enough about
> them to make a decision to go that route. This is only my third mirror.
> Succeeding on the simplest terms, ie. a Dob/Newt is probably going to be a
> challenge as it is without trying the exotic designs. 
> 
> Clear skies,
> Jerry 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
 


Mike Conron 
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