I make glass beads (also called lampwork),using long rods of glass and a torch with a flame that burns at 2500 degrees. A mixture of propane and oxygen produces the flame and by adding or reducing the amount of oxygen sent to the torch, different qualities or colors are the result. Different types and/or colors of glass react in different ways and sometimes you never know what you will see when the kiln opened!
This picture is a closeup of a bead I made and the webbing effect of the ivory glass on the right side is the result of a reduction in oxygen.
Trish (aka Funkey)