A device for adding controlled amounts of moisture to one or both sides of a copy sheet. The device includes a pair of water jets, a reservoir for storing a quantity of liquid and connected to the water jet, a pair of generally cylindrical, pressure rolls, each having an outer cylindrical surface with the rolls being aligned with respect to one another along their axes so as to define a nip between the outer cylindrical surfaces, and a controller for controlling application of water from the water jets to selected portions of each sheet passing thereunder before each sheet enters the nip formed between the outer cylindrical surfaces. Alternatively, the water jets could apply the liquid to the cylindrical surfaces of the pressure rolls.