An apparatus for the wet processing of photographic sheet material comprises at least one treatment vessel (12, 12', 12") having upper and lower openings (17, 18), one of the openings constituting a sheet material inlet and the other of the openings constituting a sheet material outlet, the inlet and outlet defining there-between a substantially vertical sheet material path (20) through the vessel. The vessel comprises a pair of rotatable rollers (28, 30) biased towards each other to define a nip (36) there-between through which the sheet material path extends. The apparatus is characterized in that the rollers (28, 30) are axially offset relative to each other; and each roller is in sealing contact along its length, at least between the limits (56) of the nip (36) with a stationary sealing member (38, 39).