which slides on the film 17 as the rear wall 8 is pivoted the sliding surface 12 is composed of the same metal for example steel or preferably aluminum from which the whole of the rest of the rear wall is produced an elastic or springy element 22 is provided in order to ensure a permanent and elastic contact between the rear wall 8 and the film 17 and in order to avoid printing ink penetrating through between the rear wall 8 and the film 17 the element 22 is a solid material cushion which is composed of a plastic foam for example polyethylene terephthalate foam pet foam or ethylene propylene diene rubber foam epdm foam and which as an underlay for the film 17 is disposed between the latter and the concave surface 23 of the fountain base 7 the solid material cushion 22 and the film 17 can be inserted into the doctor type ink fountain 4 one after the other or instead can be joined together in a sandwich structure and inserted into the doctor type ink fountain 4 in one piece the solid material cushion 22 is compressible in such a way that both in the first position and in the second position as well as in every intermediate position of the rear wall 8 between these two positions it presses the film 17 against the rear wall 8 the prestressing action exerted by the solid material cushion 22 can be seen in fig1 a and 1b by using the small reversible deformation of the film 17 and of the solid material cushion 22 in the region of the sliding surface 12 the sliding surface 12 is forced a little into the solid material cushion 22 so that the latter and the film 17 lying above.