Abstract: In an offset printing apparatus one arranges in the "channel" of the printing plate cylinder a further segment for improving the emulsion and for reducing the time-interval between "stripping" and "scumming," which is provided with a plane, water-conducting and ink-repellent plate, preferably of polished chromium steel. In the course of the rotation of the printing plate cylinder, this segment, designated preemulsifying segment, is wetted by the dampening form-roller of the dampening unit with water which is emulsified by contact with the subsequently arranged ink form-rollers, before same come in contact with the printing plate of the printing plate segment.As a result of the arranging of the emulsifying segment, the time-interval between "stripping" and "scumming" can be quadrupled and the amount of water required can be reduced.