Franking machine

A franking machine is disclosed in which printing of a franking impression is effected by exposing a layer of micro-capsules containing ink to light to thereby cause hardening of the exposed micro-capsules and then subjecting the layer to pressure to rupture the un-exposed micro-capsules in the presence of a developer with which the ink reacts to become visible. The layer of micro-­capsules may be coated on envelopes (21) or label tape (30) during manufacture or by coating means (36) in the franking machine (10, 11). The developer may be applied as a coating in a similar manner. Alternatively one or both the micro-capsules and the developer may be carried on a transfer film (31) brought into contact under pressure (34, 35) with a mail item (30) after exposure (33) of the film.