Earlier this week Bob Guenter and Jeanne Kent were wondering why
float glass was behaving badly when fused or melted in a kiln.
Float glass has two different quality faces. Apparently this is a
result of the manufacturing process -one side is the "tin" side and
the other the "up" side.
If you cut a piece of float glass, flip one section over, and paint
on a silver nitrate stain, and fire both at the same time, you'll find
the stain quality quite different after firing.
The bothersome solution is keeping track of the "best" side during
your working process.
Also----if you're fusing, the annealling temperature ranges change
after the first firing. This holds for regular window glass as well.
Maybe there's a web site at Corning Glass that will have more
details. Anyone know?