Flatlander
My understanding is that 'flowing' glass is a bit of a myth. A lot of glass from before the industrial revolution (in fact, before Pilkington developed the molten lead flow process) was made by spinning blown glass into discs. Even when cut into panes one edge was likely to be slightly thicker than the other - resulting in the dubious claim that it has flowed over time.
As for the 'fact' I was taught in school, that glass is a supercooled liquid (hence 'explaining' its flow), that turns out to be very dubious too. Glass (which refers to a particalar state of matter, rather than a particular substance), is any solid that does not have a defined crystalling state. For this reason it has properties that can be quite different from those of other, crystalline, solids. Apart from this peculiarity, however, all glasses seems to possess all the other properties we'd expect of solids - indices of brittleness and toughness, expansion and contraction due to heating and cooling, quite specific melting points, and so on.
I'm way too lazy to look up internet references (and rather bad at that sort of thing, too) but gathered most of my, albeit surely slightly garbled, information on this by a classic popular science text, The New Science of Strong Materials by J E Gordon. It is, amazingly, still in print after all these years, and available on Amazon. I also recommend its more general companion book Structures. They were published in 1976 and 1978 but haven't dated at all.
cheer
the sunshine warrior
