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bonding plate glass for mirror blank.

Started by jjam47, 05/02/2010 09:46PM
Posted 05/02/2010 09:46PM Opening Post
Hello all,
I'm planning to make a 16" mirror for a dob and was wondering why I couldn't bond two pieces of 3/4" plate glass together for the blank.I can't find much discussion anywhere regarding this idea and I'm afraid it's probably because it's not a real good idea for some reason.Possibly because of the thermal properties of the glass? could anybody out there shed some light on this Idea.(No pun intended). Thank's.
Posted 05/02/2010 11:11PM #1
The problem is, the two pieces of glass when bonded, will not expand and contract at exactly the same rate. Any stresses that are in the glass will also cause unequal changes. This would make the figure almost impossible to predict as the temperatures change.

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Posted 05/03/2010 09:06PM | Edited 05/03/2010 09:09PM #2
Perhaps bond some glass spacers inbetween the two discs. Such a sandwich blank should have greater stability both physically & thermally, yet still with low weight & cost.