The contrast between grease and water is essential in which type of printing technique?

The contrast between grease and water is essential in the lithograph printing technique. Lithography is based on the principle that oil and water do not mix. In this process, a design is created on a flat stone or metal plate using a greasy substance. When the plate is treated with water, the non-greasy areas (where the design is not) will absorb the water, while the greasy ink will adhere only to the design itself. This separation allows for the transfer of the image onto paper, making lithography a unique and effective method for reproducing detailed images.

In contrast, offset printing, screen-printing, and letterpress use different mechanisms and do not rely primarily on the interaction of grease and water for their process. Offset printing involves transferring ink from a plate to a rubber blanket, then to paper, while screen-printing uses a mesh to transfer ink directly onto the surface. Letterpress involves pressing inked movable type directly onto the paper. Each of these methods has distinct qualities that separate them from the lithographic process involving the specific interaction of grease and water.