Developed based on extensive physical and mathematical modelling, the SORG® colouring forehearth provides optimum colour homogeneity over a wide range of operating conditions.
The colour concentrate or frit is metered by a gravimetric feeding device and deposited at one or more locations on the glass surface at the beginning of the colouring system. For installations with throughputs of up to about 70 t/24h, the main mixing is done by two large-diameter, four-paddle stirrers, installed in-line at the start of the mixing area.
A system with two skimmer blocks and a wall forces the glass vertically through the stirrers. Additional mixing is provided by two banks of spiral stirrers that act as brakes to slow down the fastest forward current, effectively increasing the time available for natural mixing of the coloured glass.
For forehearths with larger tonnages, mixing occurs exclusively via spiral stirrers arranged in multiple rows.
A CONTI-DRAIN® in the stirrer zone helps speed up the removal of coloured glass during a colour change. To prepare glass for the production process, conventional cooling and conditioning zones are necessary after the stirrers.
The times needed to change from flint to colour and vice-versa depend on many factors. Typical colouring times are from 2-4 hours. De-colouring takes from 8-16 hours. Through the use of the drain mentioned above, these times can be shortened.