The primary mirror in my SW 12" reflector is made of pyrex. It was not provided with cooling fans at manufacture as it is claimed that it will match ambient air temperatures fairly quickly. I have not tested this claim with any diagnostic equipment but I have not needed to add a fan at this stage.
Another BAS member has the 14" version of my scope and he has added three fans under his primary mirror as well as digital temp readouts.
I am sure that my mirror wasn't hand blown......
