, 16% 
, 8%CaO, 4% MgO which
lowers the glassification temperature to something useful.
. This means 
. Then a = 
so 
. Ordinary
glass at room temperature is extrapolated to have 
.
ordinary glass composition is: 72% , 16% , 8%CaO, 4% MgO which
lowers the glassification temperature to something useful.
Strainpoint ( 
) is 
where it can cool at a reasonable rate.
510C is the annealing point where internal stresses are relieved in a few minutes.
700C is the softening point where lumps flow under there own gravity in a few minutes time.
1000C is the working point where glass can be blown.