Lithographers are responsible for transferring images onto metal plates. They are able to do this with basic chemical principles. Publishers use the metal plates lithographers develop to transfer text or graphics to paper in the modern printing process.
To begin the lithography process, skilled photographers take pictures of the text or graphics to be reproduced in printing. They develop negatives of each photograph they take. Lithographic artists touch up these negatives as necessary. Once the lithographer has the negatives, he can start the plate making process.
The first thing lithographers do is coat the metal plate with a solution that is highly sensitive to light. They then position the negative on the treated plate. The lithographer then exposes the negative to ultraviolet light. This transfers the image on the negative to the plate.
Once lithographers have the image they need on the plate, they treat the plate with additional chemicals. These chemicals get rid of the areas that were unexposed and which don't contain part of the transferred image. Some plates do not require this chemical processing due to technological advances.
Some specialized lithographers, known as routers, manually remove any metal on the plates that chemical processing doesn't remove. Other lithographers, known as finishers, change the darkness or lightness of the images in order to get the best quality duplicate during printing. After these lithographers complete their work, the plate is ready to use.
To use a lithograph plate, lithographers and publishers coat the original plate with water. The water sticks to the area of the plate that is not part of the image due to the chemical processing. The publishers and lithographers follow this with a thin coat of oil-based ink. Oil and water molecules do not like to bind and repel each other. As a result, the ink gets pushed to the area of the plate that has the image.
Following the inking of the plate, the lithographer rolls a rubber cylinder over it. The rubber cylinder squeezes away the water but picks up the ink. The cylinder is what rolls over the paper or other medium on which the image needs to be placed.
A problem with lithography is that computers have made it possible to reproduce images without any plates at all. Lithography jobs have become less prevalent as a result. Those interested in lithography must stay abreast of technological advances to be hired and maintain a career.