A paper curl reduction process is conducted by applying an aqueous dye or pigment ink in an image-wise fashion to a side of a substrate and by applying a clear aqueous liquid to the opposite side of the substrate. An ink printing device includes at least one printhead for applying an aqueous ink to one side of a substrate to form visible images and at least one applicator for applying a clear aqueous liquid to the opposite side of the substrate. A paper curl reduction process is also conducted by applying an aqueous dye or pigment ink and an optional clear aqueous liquid in a selected image-wise fashion by a thermal ink jet printing method to both sides of a substrate to achieve duplex ink jet printing with visible images on two sides of the said substrate.