CompuServe Messages

PMJI, Thanks for an informative discussion. I love opal, but am strictly an amateur cutter. I haven't dared to spend money for really good stuff yet<g>. >> Knowing something about valuation has helped me immensely in deciding >> how to orient and cut particular pieces of rough. <sound of palm hitting forehead> One of those things which are obvious after someone else says them. Thank you. On a different subject – >> I suspect the reason some opal cracks has more to do with the >> structural formation process; referring here to stained glass >> again…handblown glass is much more likely to contain internal >> stress flaws than manufactured glass. This made me wonder if there's a way to temper opal<g>. But it reminded me of a question you are probably well qualified to answer. When cutting obsidian (in the form of "apache tears"), I find that some of it is so highly stressed that it literally explodes when cut. Since I used to do a little glassblowing (soda, pyrex, and quartz) for laboratory equipment, I know about tempering and wondered if anyone had tried it with obsidian. Do you have any rules of thumb for getting the right temperature and cooling rate without elaborate equipment? (elaborate being anything more than a propane torch.) Al