There are many other names for lithographic printing and these include planographic, lithography or planographic printing. This type of printing works on the principle that water and oil do not mix. Dissimilar to intaglio and relief printing where the non-image and image areas are at varied levels, there is a single surface in lithography. In relief printing and in intaglio, the image regions that need to be printed are slightly raised while the non-image regions are at the base surface which is generally lower in comparison to the image regions. Nevertheless, in lithography, the non-image and the image regions are at the same level with the printing surface being absolutely flat.
The Work Procedure of Lithography
Lithographic printing is a very simple procedure consisting of a few steps that need to be followed in converting a text or image into a printed page. The plates used in this form of printing have a much roughened structure. They are also coated with light sensitive or photosensitive emulsion. The emulsion is basically a suspension of a couple of chemicals that cannot be blended together. Margarine or butter is the best household example of an emulsion. There are two methods of making the plates. One method is exposure from a source of light with film on the top of the plate or with the use of a machine that exposes the plate and using lasers from computers. Any of these ways help in creating a sort of photographic negative of the image, brings in the emulsion and then transfers the positive image to the emulsion.The emulsion is chemically treated for removing unexposed parts of the emulsion. The final step is the same as developing a film at the photo laboratory.
The Main Technique
During the process of making the printing plate, printing image is rendered water repelling or hydrophobic and grease receptive. On the other hand, the non-printing regions are rendered ink repelling and water attracting or hydrophilic. At the press, there is a plate cylinder on which the plate is mounted. As the cylinder rotates, it comes into contact with rollers that are completely wet because of the dampening solution adhering to the negative or rough parts of the image. The plate then comes into direct contact with a roller that is ink-coated adhering to the positive or smooth part of the image. In case this image is transferred to paper directly, it would make way for positive image, but then the paper might get moistened. Therefore, there is a cylinder used to be rolled over the plate. This cylinder features a rubber surface known as blanket that squeezes away the water and pick the ink. The cylinder is rolled on paper making way for ink. The entire procedure is known as offset lithography due to the fact that the image is offset to the drum prior to being applied on paper.
Lithographic printing has a number of applications in the recent times. There are many artists that make the effective use of lithography for expressing their creativity.