| abstract |
Two concentrated solutions (A and B) are used, together with diluting water (W). One concentrate, at a pH below 7, contains hydroquinone, sulphite and sodium formaldehyde bisulphite, whereas the other contains alkali, buffer substances and complexing agents if required. Both concentrates are free from bromine ions. The two concentrates are separated and a variable proportion of water is added to each at the same time as a portion of film to be developed is introduced into a developing tank (11). The concentration of regenerating mixture and the addition of water are controlled in accordance with the machine throughput, i.e. the concentration is high when the machine throughput is low and vice versa. The concentration is regulated by time-controlled proportioning pumps (5, 6, 7) and a three-way valve (8) in the line supplying water for dilution, the valve (8) conveying the water either to the processing tank (11) or back to the proportioning-pump inlet (16), depending on the position of the valve (FIG. 1). |