What is the role of nitric acid and gum arabic in lithography?

In lithography, the role of nitric acid and gum arabic is indeed to create the greasy surface necessary for ink application. The process of lithography relies on the principle that water and grease do not mix. By using nitric acid, the surface of the lithographic stone or plate is treated to enhance the greasy characteristics of certain areas, allowing for effective ink retention in those regions while repelling water. Gum arabic acts as a protective agent to keep the non-image areas of the plate from attracting ink, ensuring that only the intended greasy areas will attract the lithographic ink when applied. This interaction is fundamental to the effectiveness of the lithographic printing process, distinguishing between image and non-image areas and allowing for the precise reproduction of images.