Litografiamenetelmät

Litografiamenetelmät, commonly known as lithography, is a printing technique that relies on the antipathy of oil and water. This principle, also known as oleo-hydrophobia, is the foundation upon which all lithographic processes are built. The image is drawn on a flat surface, typically a limestone slab or a metal plate, using a greasy or oily substance, such as a lithographic crayon or tusche. The surface is then treated with a solution, usually a gum arabic and nitric acid mixture, which makes the areas that were not drawn upon hydrophilic (water-attracting) and the drawn areas remain oleophilic (oil-attracting).

When the surface is dampened with water, the water adheres to the hydrophilic areas and is repelled by the oleophilic areas. Subsequently, an oil-based ink is rolled onto the surface. The ink adheres only to the oleophilic drawn areas and is repelled by the damp hydrophilic areas. Paper is then pressed against the inked plate, transferring the image onto the paper. This method allows for detailed and nuanced images, including tonal gradations and fine lines, making it suitable for artistic prints and commercial reproduction. Modern lithography often utilizes aluminum or polyester plates instead of stone, and is a key process in offset lithography, a widely used commercial printing method.