Intaglio, relief and surface printing

Traditionally, printing methods are divided into the main groups of intaglio, relief and surface printing, according to the techniques on which printing is based. Intaglio prints normally use a metal plate, which is prepared so that the ink lies in the furrows and grooves in the plate. The principle is that the ink is not held on the polished surface but only adheres where there are lines, depressions or other types of incision. During the inking process all excess ink is removed. When a soft, damp sheet of paper is run through a press together with the plate, the paper is forced down into the grooves and absorbs the ink. The metal plates can be prepared in various ways and with various tools, by scratching, pricking or scraping marks directly into the smooth metal or by covering the plate with what is known as an etching ground, e.g. a layer of wax, and incising the design into this wax layer.The plate is then placed in an acid bath and the acid bites into the metal wherever it is not protected by the ground. Etching allows a number of methods of preparing the surface of the plate by using an aquatint ground or through direct treatment with acid in what is known as open-bite.

Munch used the term 'radering' for all forms of intaglio prints and did not specify the technique or type of tool used to prepare the plates. The term 'radering' has been retained in the Munch Museum's catalogues, although this is often supplemented by a more detailed description of the technique used.

Relief prints, as its name suggests, is based on the opposite principle, where it is the raised parts of the plate which take the ink and produce the impression. This method is almost solely associated with woodcuts, or the closely related lino-cuts, where the surplus, light areas are cut away. During the nineteenth century, woodcuts were normally carved in the end-grain of the woodblock, enabling large editions to be printed without wearing down the block excessively. The technique was frequently used for illustrations in books and papers, carved by skilled craftsmen copying photographs or works of art. Munch was one of the first modern artists to carve along the grain instead of across the grain, something which also made it possible to produce large format woodcuts. He used almost all types of wood and his surviving blocks include rough planks in spruce or pine, primed blocks in oak, mahogany and other hardwoods, hardboard and wood veneers. His tools included gouges of various thicknesses, pointed and rounded as well as broader chisels for removing large areas. He also often used a fretsaw to cut blocks into sections for colour printing.

Surface printing is normally associated with lithography, printing from stone. Lithography was invented by Alois Senefelder at the end of the eighteenth century and quickly gained in importance as a commercial printing method. It was used by several artists in the first half of the nineteenth century but really took off towards the end of the century. Here the printing block is a thick, porous limestone, which is ground to provide a smooth and even surface on which the artist can draw directly using lithographic crayon or tusche. Then the stone is prepared by a fairly complicated chemical process which fixes the drawing to the surface of the stone.

Before inking, the stone is wetted thoroughly so that water is absorbed into the porous stone, with the exception of the part of the surface where the drawing makes it water-resistant.Then the stone is rolled with a greasy ink, which does not adhere to the places where the stone has absorbed the water. One problem with lithographic stones is that they are expensive, besides being heavy and unwieldy. They are also fragile and can easily be chipped or smashed. Consequently, there was great interest in discovering new materials to replace the expensive stone and good results were obtained using specially prepared zinc plates. In commercial printing these soon became more common than the traditional stones. Prints from zinc plates are often called zincographs. Munch also used lithographic zinc plates on a few occasions.

Another method which allowed artists to avoid working with the unwieldy stones altogether was to draw on paper and have the printer transfer the drawing onto a lithographic stone. Such transfer techniques were developed at an early stage and a number of special types of paper were produced to ensure the best possible result. A skilled printer, however, could obtain perfect transfers from normal paper and Munch preferred to place a relatively thin sheet of paper on a textured base before drawing on particularly grainy transfer paper. Many of his drawings for such transfer lithographs have also been preserved.

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