Re: Thermal glass problems

To: neon-l@netcom.com
Subject: Re: Thermal glass problems
From: dead@netcom.com (John Anderson)
Date: Sun, 18 Feb 1996 20:49:49 -0600
Reply-To: neon-l@netcom.com
Sender: owner-neon-l@netcom.com

>piece that was supposed to be a whole piece. Annealing glass is a complete
>science in an of itself. You gotta gauge for this one, Morgan <g>.

I actually do!  A polariscope.  You can buy them, but I made mine from two
sheets of polarized film and a piece of frosted glass.  It's invaluable
when doing repairs on clear glass units someone else made.  Lots of strain
usually means the unit will splinter when you try and cut off a 'trode.  A
quick anneal in that case saves lots of heartbreak.

It's also a great way to learn about stress in neon glass.

     -John


Make a polariscope yourself:



    ----------------------------     polarized sheet (camera store)


      =======================       <----  clear neon glass


     ----------------------------         polarized sheet
  __________________________________     (positioned perpendicular to the first)
      (frosted glass, white plex)
        ^^^^^^^^^^^^^^^^^^^^^^^
            light source
   (a loop of 6500 white works great!)


I have about a 6" space between the two sheets, which are sandwiched
between glass for durability.  If the two polarizing sheets are
perpendicular, then they cancel out the light from below.  Strain in glass
defracts this light, showing up as bright-white streaks & patterns.