According to how the matrix holds the ink, two different methods are used for engraving: the relief (woodcut, linocut) and intaglio; this latter process falls into two groups: direct engraving (burin,drypoint, black manner or mezzotint and stipple engraving) and indirect engravings (etching, aquatint and soft-ground etching or vernis mou ).

Relief type printing includes the engraving techniques that create a matrix inked at the moment of printing on the raised parts, while the depressions, the furrows, are not inked. The artist engraves the parts of matrix that will be white on the paper; while the parts in relief are inked (like a rubber stamp) so that only they will be printed on the paper.

The word intaglio defines all those engravings whose matrices hold the ink in the furrows and yield it to the paper during printing. The furrows can be carved directly on the surface with special tools - direct method - or using an acid which bites into the metal - indirect method.

| Woodcut |

Woodcut is a relief process. The matrix is a block of wood that can be cut either longitudinally as planks, or cross-grained, when it is cut transversally. Longitudinal blocks are softer and give a less precise line while the wood of the second kind, made by uniting various carefully selected pieces, is fine-grained and harder. Its thinner and closer lines produce a design rich in detail. The drawing on the block is cut in relief. The parts cut away with the gouge are white in the finished print while those standing in relief are black. The first prints on paper done from wood blocks were made in China and date from the eighth century. According to some documents, in Europe the first woodcuts-simple images of saints, and playing cards - date back to the late fourteenth and early fifteenth centuries. The ancient religious prints were essentially linear, often embellished by hand coloring. The invention of movable type printing, which applied the relief process to the letters of the alphabet, and the subsequent development of publishing represented a field of applications and uses for woodcut. In the late fifteenth century the production of books illustrated with woodcuts spread especially in Italy and Germany. However, even the most sophisticated images were anonymous or done by artists who can be identified only hypothetically, until Dürer, with the aid of the technical progress of the printing press, was able in just a few years to develop an idiom for the new art. He renewed the technique's possibilities for representation using the rules of Renaissance art, creating compositions of great openness and complexity. The end of the eighteenth century was another period of renewal, when the new technique of engraving on cross-grained blocks brought about a radical change in the way woodcuts were conceived, and again when Gauguin ushered in the modern era in woodcut.

| The Linocut |

A characteristic of modern relief printing is the use of materials other than wood to create matrices, including linoleum. Linoleum is made of a combination of linseed oil, ground cork, and gum spread on a canvas or burlap backing, creating a smooth, compact surface that can easily be engraved using gouges. This technique is not different from woodcut as the finished prints have the same aspect, but linoleum is easier to work than wood, as there are no knots and it is flexible, offering itself to fluid, spontaneous drawings. This material was patented by F. Walton in 1863 and has been used to make matrices for relief printing since the first years of this century. Kandinsky and some Expressionists engraved on linoleum. Matisse was fascinated by its ease in working and used it in the simplest terms possible, creating a series of engravings of pure white lines on a black ground. Picasso too used linoleum to do a number of colored linocuts between 1958 and 1964. In Italy, M. Maccari is a major exponent of linoleum engraving. The evolution of linocuts is particularly interesting; it was developed in Poland after the second world war, where Grabowski and Starczewski analyzed the structural elements of its graphic language, while Gielniak and Fijalkowski exploited it to evoke surreal and sometimes metaphysical atmospheres.

The printing of wood- and linocut is done using a vertical printing-press which works like a normal press. The ink is deposited on the relief. Wood- and linocuts can also be printed manually by mounting the matrix on a board, placing a sheet of paper over the parts in relief and rubbing the back of the paper with a spoon or a bone stick.

| Burin or line-engraving |

This engraving technique is the most ancient procedure; its name is linked to the tool used to engrave metals. Dating back to the first half of the fifteenth century, it derives from techniques adopted by medieval goldsmiths, who used the burin to engrave thin layers of metal, usually silver, then filled the carved lines with a black substance called niello (nigellum) to bring out the design. When to check the chiselling a sort of thick ink was poured into the carved lines instead of the niello, it was discovered that the drawing could leave its print on a wet sheet of paper producing the first burin impressions. Niello means both the engraved thin layer of metal and the print on paper. The chalcographic technique, called line-engraving, evolved when the engraved matrices were printed on a sheet of paper using a printing press. The burin is a thin steel bar with a sharp end cut crosswise and having different types of sections: square, triangle, rhomboid etc. A wooden handle shaped like a half-sphere can be adapted to the artist's hand so that he can exert a constant pressure with his hand and press the tool with his finger at the same time. The inclination of the burin on the surface depends on the kind of tip used. During engraving, the plate is laid on a leather cushion filled with sand to keep it from shifting under the pressure of the artist's hand but so that he can move it as he works. To create curves, he holds the burin stationary and rotates the cushion. As the burin gouges the metal it raises shavings called burrs, that are removed at the end of the work. The engraved lines hold the ink for printing. The result is a drawing with sharp clear lines that constitute the main characteristic of this technique. In the fifteenth century, artists such as Mantegna, Schongauer and Dürer engraved their drawings directly onto the copper giving the burin an autonomous expressive role. In later centuries it was mainly used to reproduce great paintings, and in the nineteenth century to illustrate historical events and customs. Only at the end of the last century was engraving as a means for creating art discovered again, and the burin acquired artistic autonomy.

| Drypoint |

Drypoint is a direct intaglio technique for engraving metal without the use of acids. The tool usually used is a sharp stylus with a steel or diamond point. Varying the pressure on the tool causes a variation in the depth and width of the lines, that after printing will yield a more or less rich effect on paper. In this technique, the burrs crested by the pressure of the point are left to hold the ink, giving a soft, thick printed line which is the main characteristic of this style.

The burrs are soon removed during the cleaning of the plate or flattened by the press. Thus the marks lose their printing strength after only a small number of copies.

Because of this last characteristic, drypoint has never been used as a reproductive technique.

| Stipple Engraving |

Stipple engraving is an direct technique of engraving, that is without acids, used especially on copper or zinc plates. Differently than in the chalcographic technique, a stippling tool is used to create images with dots. The stippling forms a ground of burrs on the plate and, as in the dry point technique, the artist can either remove or leave them, depending on the effect he wants to achieve.

| Black Manner or Mezzotint |

This technique, also called mezzotint, was invented by the German Ludwig Fon Siegen (1609-1680) and saw its greatest development in England in the eighteenth century. It achieved its full formal perfection when the engraver Blooteling invented the rocker, wiegen in German, berceau in French, a tool that ever since has represented the classical means for covering the plate with a mesh of small burred dots. The mezzotint emerged in a period when reproductive engraving techniques were verypopular and it was primarily used to reproduce paintings, because it permitted subtle effects of shading and highlights . It flourished throughout the eighteenth and nineteenth centuries, until its place was taken by the more sophisticated photographic techniques for reproduction. Today only few engravers use it as an autonomous means of artistic expression, because it is a tiring and slow method of engraving. After preparing a perfectly smooth plate of annealed copper; the artist prepares the ground with the rocker invented by Blooteling. This is a small steel blade with a curved edge and sharp pointed ends. Holding it by its central handle, the engraver rocks it slowly forward with a waving movement, so that it leaves small dots like those created in drypoint on the copper. The matrix is ready when the plate is completely covered by dots. In mezzotint, the painter-engraver inverts the order of the creative act, which usually is a process of addition. Here instead he removes bit by bit the black from the rough ground, moving through shades of gray toward white.

He uses two tools : the burnisher and the scraper for the ground. The burnisher is usually made of hard tempered steel and is shaped like a small blade. The number of copies printed that can be made from a mezzotint plate is limited to no more than forty.

| Etching |

Etching is the first indirect technique of engraving used as an expressive means since ancient times, as it gives the artist great creative freedom, without the long apprenticeship that characterizes other means of artistic expression.Its origin most plausibly dates back to the middle ages, when nitric acid (aqua fortis, as the medieval alchemists called it) was used to etch decorations into weapons and armor. Later, in the late fifteenth and early sixteenth century , the technique and name were adopted by engraving artist. The sequence of engraving is as follows: after cleaning and smoothing the surface, the artist covers it with a thin layer of special wax, which will be darkened with lamp-black to make the wax more resistant to the acid and the engraved lines more visible. Then the artist uses a stylus to press through the wax and uncover the metal, drawing the lines that will compose the image. Once the edges and the back of the plate are protected, it is immersed in a basin containing some diluted acid.

The most commonly used types of acid are nitric acid and perchloric acid. Nitric acid is almost always used on zinc plates, and perchloric acid on brass and copper. During the "biting", that is the acid's corrosive action, the acid creates small bubbles that settle on the carved drawing. As they form, the artist removes them using the feather of an aquatic bird ( which are the most resistant type), in order to obtain a regular line. Moreover, during the chemical reaction perchloric acid deposits in the furrows a rust-coloured pulp which impedes the biting; so that plates are often washed or held upside down so that the pulp falls into the basin. Using a different concentration of acid and varying the biting times different kinds of lines and results can be achieved.

| Types of biting: |

1) simple - after one immersion in the acid, the lines have all the same strength: the shades and color gradations are created by the more or less dense network of lines.
2) layered - after successive multiple immersions. The engraver immerses the plate in the acid a first time, then covers with a protective wax the lines that must be thinner and lighter in the print. Then the plate is immersed again to obtain thicker lines and the procedure is repeated as many times as required to obtain wider and deeper lines. In the print the sharp edges due to the different moment of biting will be clearly visible.
3) addition - when the darker lines are the first to be engraved and thinner and lighter lines are added step by step through a series of immersions. This method creates not only sharp lines, but also areas of soft shades and nuances, because the artist can change any part of his work until the moment of biting.

Among the first to use this technique are Urs Graf, a goldsmith from Basil and the author of the first dated print (1518), and Dürer, who engraved six iron plates, including The Cannon (1518). However, it was Parmigianino who realized the possibilities of the technique and brought it to perfection. Original etching spread quickly throughout Europe, taking the place of xylography and partly of the burin, with Rembrandt its major artist. It has to be stressed that original etching is different from reproductive etching, started in the school of Raffaello da Marcantonio Raimondi and created to reproduce the master's works. Among the major engravers of the seventeenth century are the landscape painters Jacques Callot and Claude Lorrain in France and Stefano della Bella and Giovanni Benedetto Castiglione, called the Grechetto, the inventor of the monotype, in Italy. In the seventeenth century, engravings provided bitter and ironic comments on social miseries and contrasts. (Hogarth, G.B. Tiepolo, Piranesi, Goya, and others). In the eighteenth century lithography, a new technique, was preferred to engraving until Corot, Millet and other impressionists (Pissarro, Manet ...) rediscovered its possibilities. Many modern painters such as Picasso and Braque reached remarkable results with etching, but especially the German impressionists used it, together with lithography, for its graphic expressive strength. As all with the other engraving techniques, etching is today greatly appreciated by both artists and the public.

| Aquatint |

The aquatint is an indirect process of engraving and can be considered a technical variant on etching, as the engraving is made with an acid. It follows the same procedure as the one described for etching, but the final effects, obtained with a porous plate, are similar to water-colours. The texture is created by dropping grains of bitumen onto a hot plate, which melt and stick to the surface, forming a more or less thick ground. Aquatint is a tone process rather than a line method : instead of forming an image with an organized series of lines, it creates areas of controlled shapes and contrasts. To do so, the matrix is specially treated to obtain a rough surface able to hold the ink. This roughness is called granulation. The biting operates in the hollow spaces. The longer the biting time, the darker the background, thus achieving different nuances of gray simply by varying the time of immersion.

| Vernis Mou ( Soft-Ground Etching ) |

This is a particular variety of etching; instead of covering the surface with the usual resin, the artist spreads a composition of warmed resin and tallow using a brush or roller, creating a softer ground. He than places a thin sheet of paper on the plate and draws on it with a sharp pencil. Under the pressure the soft wax sticks to the back of the paper, and comes off with it when the sheet of paper is removed. This technique is also called crayon or color-engraving because it produces an image similar to drawing. Different kinds of pencils and paper yield a variety of effects.

This technique dates back to the eighteenth century (J.- Charles Françoise 1717 - 1759) and was invented to imitate the rough line of the pencil as well as the softness and gradation in shade of pastel-colours. Today it is almost always combined with other techniques.

Copperplate prints are made using a sticky kind of ink, with the plate being warmed on a stove.

The basic stages of copperplate engraving:

- spreading of the ink

- daubing the ink

- removing the excess ink

- cleaning and burnishing the plate

- cleaning the corners

- immersion of the sheet of paper

The paper for the intaglio process of engraving is of a special kind: it contains little glue and no wood fibres. It is similar to blotting paper and must be wet in order to adhere better to the inked depressions.

| The printing process |

The plate is inked before the printing of each sheet of paper. The printing process is done with a hand press on a movable plane passing between two metal rollers.
Between the cylinders pass :
a) the plane
b) the inked plate
c) the wet sheet of paper attached to the plate
d) a blotter to absorb the water from the paper squeezed out by the cylinders.
By pulling a lever, the entire rolling process is set into motion.