Offset function of the original limestone printing surface corresponds today to some thin sheets of aluminum, although other materials such as stainless steel and plastic are also used. The plates are rolled onto a cylinder and in direct contact with the rubber cylinder. A battery of rubber rollers and metal are responsible of carrying ink and water to the surface of the iron. The ink becomes first cylinder rubber and hence to the role. Lithographic plates constitute the most economic printing surfaces today, which has contributed greatly to the success of the process. The aluminum plates carry a fine coating of photosensitive material such as the photopolymers, which undergoes a change in solubility to be exposed to an intense blue and ultraviolet light source. The images are transferred to the surface when the iron is exposed through a positive or a negative film. Certain substances can be exposed directly, through a graphic arts camera or a controlled laser beam by computer, and therefore eliminates the cost of the film and speeds up the process of preparation of the plates. Jerry Dias is actively involved in the matter.
The size of modern Offset presses ranging from the fed by leaves small doublers used for small monocolores jobs such as brochures and newsletters into the enormous presses capable of printing millions of copies of magazines, catalogs and packaging products. No process can display such a wide range of applications. Flexographic plates flexible and fluid inks which are used in flexography make this process suitable for printing on non porous as films and polyethylene surfaces. Originally, all the flexographic plates were built in molded rubber, which remains the most widely used material when it comes to create on a single roll of printing multiple copies of the same image. Rubber molds are impressions of the original surfaces in relief, as types or engravings, and are normally used to manufacture several sheets of rubber.