Soft glass?

Found this on google:

This is the most common commercial glass (90% of total production), and also the least expensive. The chemical and physical properties of soda-lime glass are the basis for its widespread use. Soda-lime glass is primarily used for bottles, jars, everyday drinking glasses, and window glass. It usually contains 60-75% silica, 12-18% soda, and 5-12% lime. Soda-lime glass is resistant neither to high temperatures nor sudden thermal changes, nor to corrosive chemicals.
I didn't think you could have a bowl out of plate glass that didnt shatter when you lit up like first time .I'm familar with plate or soda lime glass, Pyrex/borosilicate glass, also BK7, there's one or two more that astronomer's use to make their equipment. nothing like:tokin::tokin: and staring out into space when you have 254mm dia. telescope. I know my scope has a 10" mirror made of Bk7 which is in between plate and pyrex in many areas including price thermal expansion. I'm not sure what works other then pyrex but I know plate aint great.
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