Offset lithography operates on the principle that grease (ink) and water won’t mix. The image information being printed is placed on thin metal plates which during the printing process are continually dampened by water. The oil-based ink only adheres to the image (greasy) areas and the water dampens only the non-image (non-greasy) areas. The inked areas are then transferred onto a rubber cylinder (called a blanket) and then onto the paper as it passes around the blanket. The process is called offset since the image doesn’t go directly from the plates and onto the paper, but is offset or transferred to another surface that acts as the intermediary.