the fining zone should be prevented by the
choice of suitable refractory materials and controlling
the interface temperature to values below a certain critical
level. The glass melt entering the fining zone
should be free of grains (sand, alumina, aluminum-silicates)
that still have to be dissolved, since these grains
may generate (nucleation, or a decrease of CO2 solubility
in melt surrounding dissolving grains) new CO2
seeds interfering with the fining process.