The techniques of printmaking used in the 15th-16th centuries are divided into two major categories: relief and intaglio processes. The surface processes: planographic (lithography) and stencil methods were applied only later.
In relief processes, the negative, or nonprinting part of the block or plate, is either cut or etched away, leaving the design standing in relief. Or, instead of cutting away the background, the relief print can be created by building up the printing surface. The relief is the positive image and represents the printing surface. The most familiar relief-printing materials are wood and linoleum, but many other materials can be used, such as aluminum, magnesium, and plastics. Any metal or plastic plate incised or worked in relief can be first inked in the depressions (intaglio inked) and then surface rolled, thus combining relief and intaglio processes.
Relief printing lends itself particularly to a bold conception of design, expressed more in areas than lines. This varies, however, depending on the material used: metal allows more intricate detail than wood, for example.
Woodcut, which appeared in the 8th century in the East and in the early 15th century in the West, is the earliest known relief-printing method. In this method, the design is first either painted directly onto the wood block or pasted on it. Then the surface of the wood is cut away around the design. For fine details and outlines the knife is used; larger areas are removed with gouges. The depth of the relief depends on the design: open areas must be cut deeper than the fine details so that the roller will not deposit ink in these areas. Although woodcuts are generally conceived in bold lines, or large areas, tonal variations can be achieved with textures, a variety of marks made with gouges, chisels, or knives. In contemporary woodcuts many other methods, such as scraping, scratching, and hammering, are also used to create interesting textures.
Originally, woodcut was a facsimile process; i.e., the cutting was a reproduction of a finished design. With most contemporary woodcuts, however, the artist creates his design in the process of cutting.
As wood is a natural material, its structure varies enormously and this exercises a strong influence on the cutting. Wood blocks are cut plankwise. The woods most often used are pear, rose, pine, apple, and beech. The old masters preferred fine-grained hardwoods because they allow finer detail work than softwoods, but modern printmakers value the coarse grain of softwoods and often incorporate it into the design.
The printing of woodcuts is a relatively simple process because it does not require great pressure. Although presses are used, even hand rubbing with a wooden spoon can produce a good print. The ink used to print woodcuts must be fairly solid and sticky, so that it lies on the surface without flowing into the hollows. The printing ink can be deposited on the relief either with dabbers or with rollers. Japanese rice or mulberry papers are particularly suitable for woodcuts because they make rich prints without heavy pressure.
Intaglio printing is the opposite of relief printing, in that the printing is done from ink that is below the surface of the plate. The design is cut, scratched, or etched into the printing surface or plate, which can be copper, zinc, aluminum, magnesium, plastic, or even coated paper. The printing ink is rubbed into the incisions or grooves, and the surface is wiped clean. Unlike surface printing, intaglio printing--which is actually a process of embossing the paper into the incised lines--requires enormous pressure. The major working methods for intaglio printing are engraving, etching, drypoint, and mezzotint. Intaglio processes are probably the most versatile of the printmaking methods, as various techniques can produce a wide range of effects, from the most delicate to the boldest. The intaglio print also produces the richest printed surface, as it is three-dimensional.
In engraving, the design is cut into metal with a graver or burin. The burin is a steel rod with a square or lozenge-shaped section and a slightly bent shank. The cutting is accomplished by pushing the burin into the metal plate. The deeper it penetrates into the metal, the wider the line; variations in depth create the swelling tapering character of the engraved line. After the engraving is finished, the slight burr raised by the graver is cleaned off with a scraper. The engraved line is so sharp and clean that it asserts itself even if cut over a densely etched area. In the print, the engraved line is notable for its precision and intensity. In engraving, the hand does not move freely in any direction but pushes the graver forward in a line; a change of direction is achieved by the manipulation of the plate with the other hand. Although copper, zinc, aluminum, and magnesium plates are used--and in the past soft iron and even steel were used--the best all-around metal is copper. It has the most consistent structure and is neither too soft nor too hard.
Next to engraving, the drypoint is the most direct of the intaglio techniques. In printing, however, it represents the opposite end of the spectrum. Engraving is precise; drypoint is rugged, warm, and irregular.
Drypoint is made by scratching lines into metal plates with steel- or diamond-point needles. In this method the penetration into the plate is negligible; it is the metal burr raised by the point that holds the ink. Because the burr is irregular, it prints as a soft, velvety line. The angle of the needle has much more effect on the width of the line than the pressure does. If the needle is perpendicular to the plate, it throws burr on both sides, which then produces a thin double line; for wide lines the optimum angle is 60 degrees. Many artists use an electric graver to make drypoints. The oscillating point of the tool punches little craters into the plate. Because the line consists of thousands of these small craters, it is richer than the conventional scratched line made by the needle and stands up better to printing.
Copper plate is the best for drypoint. The plates are fragile because the burrs are easily flattened down by the printing pressure. Even a too vigorous wiping can damage a plate. Thus, unless the artist is satisfied with a very limited number of proofs (three or four), the plate must be faced with steel, a process in which steel is deposited by electrolytic means on the copper plate. This coating is very thin and, if it is properly done, the burrs are hardened without affecting printing quality. Zinc and aluminum, however, cannot be steel-faced.
Etching is a process in which lines or textures are bitten (etched) into a metal plate with a variety of mordants (acids). The metal plate is first covered with an acid-resistant coating (ground). The design is then scratched or pressed into the ground, exposing the metal in these areas. Finally, the plate is submerged in an acid solution until the desired depth and width in the exposed areas is reached.
Although the basic principle of etching is very simple, there are many possible variations that have a strong influence on the final result. The materials themselves offer a wide range of possible variations: for example, copper, zinc, aluminum, or magnesium plates can be used; and nitric acid, hydrochloric acid, or ferric chloride can be used for the etching process. Other variations include the strength of the mordants, the biting time, the kinds of grounds and the ways in which they can be worked, and, finally, all the possible methods of printing.
Although all of these matters seem purely technical, every tool or material that is used, every step that is followed, is an integral part of the creative process. The biting action of the acid is just as much part of the drawing as is the incising into the ground. The selection of the paper or the method of wiping the plate can completely change the nature of a print.
The acid bite of the plate is a critical stage in the making of an etching. The printmaker must be familiar with the characteristics of the materials that are being used. On a zinc plate nitric acid is used. In the process of biting, this acid develops air bubbles over the bitten area. Under the bubbles the acid action is slower, and, therefore, if the bubbles are not constantly moved around by brushing, the etched line will be uneven. Nitric acid also has a tendency to underbite, that is, to bite not only straight down but also sideways. For this reason, areas of dense texture must be watched very closely.
Nitric acid also can be used on copper, but, except to bite out large areas, Dutch mordant is much better suited for this metal. The action of hydrochloric acid on copper is much more even and controlled than that of nitric acid. Thus, for a bold, rough bite, nitric acid on zinc is fine; but for delicate, controlled etching, Dutch mordant on copper is preferred.