00:01
What is tempered glass and what happens during tempering of a glass? so basically this is a process of strengthening the glass against thermal mechanical stresses.
00:13
And what happens could be described actually in two steps.
00:18
So first you heat a glass block toward softening point.
00:23
However, you don't reach the softening point of a block just passing through the glass and glass transition.
00:30
Okay so you have softening if you have on the exterior of the block but internal part is still just solid okay so just below the softening point then you it is followed by uh rather rapid cooling so that cooling cycle which is normally done in air jet or in an oil bath causes different uh cooling rates so as you know that during cooling cooling we have stresses introduced to a glass block, okay? and these stresses are caused because of different cooling rates of the exterior, as you see in the picture, and the interior section of the glass, which is hotter.
01:16
And what happens is that in those temperatures, when you cool it, the rapid cooling of the surface happens, and the surface becomes solid, okay, so that in extension of time, when you have, when time comes, to the cooling of the interior section of the glass, then the exterior already cooled exterior doesn't allow any deformation or strain...