Increasing ecological constraints linked with economic advantages have
induced the recycling of cullet predominantly in the container glass
industry as well as the recycling of filter dust in various branches o
f glass production. The recycling of cullet, originating from non-refi
llable glass packaging was introduced more than 20 years ago, whereas
the recycling of filter dust originating from waste gas treatment, was
started only a few years ago. The transition from employing basically
constant raw materials to utilizing increasing amounts of recycled gl
ass as the major batch material and the introduction of filter dust as
an additive (refining agent) have imposed new challenges on glass mel
ting. Difficulties result from the incorporation and possible enrichme
nt of impurity components such as metals and halogens and furthermore
from the unknown and changing amounts of organic contaminations. Speci
al efforts will be discussed which help to improve the reproducibility
of glass melting with high portions of cullet by employing an in-situ
control of the redox state in the glass melt.