Anyone familiar with a glass from Schott called "Robax"? Apparently, very low thermal expansion and very high temp. Used for wood stove windows. American Science and Surplus (worth visiting, just for the fun of the unusual stuff they sell!) has 12" X 9" X 3/16"" inch windows (strange shape...not clear what the dimensions refer to...) but pretty darn cheap ($3.50 each). Web search indicates Robax can be easily cut (unlike tempered glass). Kind of on the thick size but may be of interest...
