are defined by nip roller pairs 11 12 and 12 15 respectively the spiral groove 10 comprises an inlet portion 10a extending from the inlet a to its center 18 and an outlet portion 10b extending from its center 18 to the outlet b as shown in fig1 the inlet portion 10a and the outlet portion 10b of the spiral 10 are interleaved and define a relatively long but compact processing path processing solution not shown is pumped into the spiral groove 10 to form a processing tank which has a processing path in the form of a spiral film not shown is processed as it traverses the spiral path between the inlet a and the outlet b a pair of rollers 13 14 are arranged at the center 18 of the spiral groove 10 to receive material arriving at the centre 18 and to direct the material away from the centre 18 and towards the outlet b rollers 13 14 are used to turn the film around sharp corners as it approaches the center 18 of the spiral groove 10 rollers 13 14 are also used to maintain the speed of the film as it passes through the processor and to drive the film out from the centre 18 of the spiral groove 10 rollers 13 14 are geared to the nip roller pairs 11 12 and 12 15 so that the film is driven at substantially the same speed film is introduced into the inlet a and is driven along inlet portion 10a of the spiral groove 10 by nip roller pair 11 12 at the center 18 of the spiral groove 10 the drive for the film is.