American Ink Jet has developed inks for two completely different printing methods that could make computer-to-plate printing an inexpensive reality. One ink is designed to print onto a diazo resin coated lithographic printing plate while the other is designed to print directly onto the aluminum surface of a lithographic printing plate. Both inks can be printed through a piezoelectric ink jet printer and are capable of producing robust images on lithographic aluminum plates. The lithographic plates produced have been projected to generate tens of thousands of offset impressions. Additionally, high resolution is ensured because the dot size for both inks is approximately 55 μm to 60 μm. The first method, in which the ink is printed onto a coated lithographic plate, is a four-step process. Step one: the desired image is printed onto the photosensitive diazo layer of an aluminum lithographic plate. As the image is printed, the ink undergoes a chemical reaction with the diazo resin coated surface. Step two: the image, now hydrophobic after the reaction, is fixed to the lithographic plate by a heat treatment. Step three: the plate is washed with an aqueous developer so that only the hydrophobic image remains on the lithographic plate. Step four: the image is rendered permanent by a post-development bake. In the second printing method, ink is printed directly onto the aluminum surface of a lithographic printing plate. In this process, the ink reacts with the aluminum surface to form a robust hydrophobic polymeric image.