Re: Tell Pyrex from Silica
Bill Marriott (btk@ix.netcom.com)
Thu, 11 May 1995 22:57:57 -0700
You wrote:
>
>I have gotten some blanks - actually they were made into convex
>
>mirrors - and I have been assuming they are pyrex. But as I look
>at them they look to good to be pyrex - no internal striations etc.
>I wonder if they could be fused silica.
>
>Does anyone know of a simple test to tell pyrex from fused silica?
>
>I've been thinking about trying to measure index of refraction, by
>focault test throught the back of the blankd (convex mirrors), but I
>don't know if I can get enough accuracy to differentiate.
>
>Which is harder. Will silica scratch pyrex, but not vice versa?
>
>Tom Clarke
>clarke@acme.ist.ucf.edu
>
How about a little destructive testing......
One way to tell if you can cut off a small piece, is to get them very
hot, and drop into cold water. Pyrex will crack, fused silica won't.
Fused silica is much harder than pyrex, and you'd think the scratch
test would apply.....at least you'd not have to destroy those blanks to
test them...
Bill Marriott
btk@ix.netcom.com