RE: [Vo]:Thermal cameras better than thermocouples for averaging temperature

[Finlay MacNab]

And I forgot,  much of the brightness of glass is from the sodium emission 
line.  Glassblowing glasses filter the sodium emission line (brilliant yellow 
light).  Much of the brightness of molten glass comes from light from sodium if 
i recall correctly.  In fact, when you put on sodium line filter glasses while 
glass blowing the glass is not bright at all.
(chemists love to blow glass... I made a bowl once... it was ugly)