a kind of engraving on metal in which the design is bitten in the plate with acid. Etching has been known since the early 16th century. Before that time, lines were engraved on the metal plate with a burin. Etching is the less laborious of the two techniques.
The first step in etching is the application of an acid-resistant ground to a zinc or copper plate. The etcher draws his design using a steel needle, allowing the point to scratch through to the metal. The zinc plate is immersed in a bath of nitric acid. (Copper plates are placed in a solution of iron perchloride.) The acid bath may involve several stages. After the first bath, the portions of the plate that were not coated with the acid resist are slightly indented. The areas that correspond to the lighter parts of the design are again covered with ground, and the plate is immersed a second time into the acid. This allows the remainder of the design to be bitten to a greater degree. Thus, after several immersions, the desired gradation of tones is achieved. To print the design, ink is rubbed into the bitten furrows, and the smooth surfaces are left free of ink. Pressure is applied to the plate, and the ink is transferred to paper.
In the broad sense, the term “etching” is often understood to include other types of engraving with acid, such as aquatint and wash drawings, which usually are used in combination with line engraving and soft-ground etching. All types of etching, especially aquatint, can, like line engraving, be used for color printing.
E. M. FARBER
Etching is generally popular among artists who have a picturesque view of the world and mix real and fantastic images. The artists are attracted to the inherent characteristics of etching: spontaneity of line and unexpected, accidental variations in tone or line that occur during printing. It is possible to obtain different prints from the same plate. The “caprices” of the drawing process, the acid bath, and the printing provide the skilled etcher with additional means for artistic expression. Repeated acid baths create a richer range of tones, and a properly sharpened etching instrument gives the lines precision and elegance. A needle or nail may be used to draw the design on a plate covered with the acid resist. Another technique is to draw the design on the metal with a brush dipped in acid. Each drawing technique results in differences in line.
An etcher may produce hairlines, patches, and soft wide lines. A free, unconstrained etched line enables the artist to achieve an extremely wide range of emotional expressiveness—from the deepest lyricism to dramatic tension. The combination of etching and aquatint (which creates gentle transitions of tone), chiaroscuro effects reinforced by the use of the dry point (which imparts to strokes a certain richness or velvety quality), the unrepeatable texture that arises as a result of repeated immersions in acid—all these elements impart to etching characteristics that distinguish it from any other type of engraving.
The first etchings date to the early 16th century. They were produced by the German masters D. Hopfer and A. Dürer. In the 16th century, iron plates were used for engraving, and in the 17th and 18th centuries, etchers used copper plates. It has only been since the 19th century that zinc plates, which are simpler to work with, have been used in etching.
The heyday of the art of etching was the 17th century. In France at this time J. Callot was producing etchings marked by a notably grotesque quality and, at the same time, a faithfulness to life. Callot, whose art is distinguished by great technical skill, was among the first to use repeated acid baths. In Holland, the work of Rembrandt in many ways was the model for the work of subsequent generations of master etchers. He combined a dynamic stroke, the rich or scarcely noticeable line of dry point, and repeated acid baths to achieve the most delicate chiaroscuro. Rembrandt discovered almost all the artistic possibilities offered by etching and used them to produce highly complex psychological characterizations, as well as feelings of tragedy and humanity. Other important Dutch etchers who worked at the same time as Rembrandt included H. Seghers, A. van Ostade, P. Potter, J. van Ruysdael, and N. Berchem. The 17th century Flemish artist A. van Dyck produced exemplary etchings. Master etchers of this period also included G. Reni and G. B. Castiglione in Italy and J. Ribera in Spain.
From the middle of the 18th century, two paths of development can be distinguished in etching: the original and the reproductive. Brilliant masters of original etching included G. B. Tiepolo, Canaletto, and G. B. Piranesi in Italy; A. Watteau, F. Boucher, and H. Fragonard in France; and W. Hogarth in Great Britain. Colored etching became popular in the 18th century.
At the turn of the 19th century, the Spanish artist F. Goya laid the basis for new directions in etching. Possessing an uncanny feeling for the medium, he combined etching with aquatint, making use of the painterly qualities of the latter. He thus achieved great emotional expression. Outstanding etchers of the 19th and early 20th centuries included J. F. Millet, C. Corot, C. F. Daubigny, E. Manet, and T. Steinlen in France; A. von Menzel and L. Corinth in Germany; A. Zorn in Sweden; J. B. Jongkind in Holland; J. A. M. Whistler in the USA; and I. I. Shishkin, V. V. Mate, and V. A. Serov in Russia.
In the 20th century, an intensive search for a new expressiveness in etching has continued. There has been experimentation with more complex and combined techniques to increase expressiveness of line, to extend the range of colors, and to expose the texture of the plate. Etching has been combined with stamping. Important 20th-century artists working in the medium of etching have included P. Picasso in France, F. Brangwyn in Great Britain, K. Kollwitz in Germany, and G. Morandi in Italy.
In the Soviet Union a large number of major artists have used etching. These artists have included I. A. Fomin, I. I. Nivinskii, A. I. Kravchenko, G. S. Vereiskii, D. I. Mitrokhin, G. F. Za-kharov, M. G. Deregus, and R. M. Gibavichius. Etching is an especially important branch of Soviet Estonian graphic art (E. Okas, A. Kjutt, V. Tolli).
K. V. BEZMENOVA
the dissolution of the surface of a solid that, in contrast to corrosion, has a practical aim. A distinction is made between etching whose purpose is to treat and change the surface shape of metals, semiconductors, glass, and wood and etching to reveal the structure of crystalline materials.
Etching for production purposes—most often a chemical process—is used to remove scale or to produce the required type of surface in metal semifinished products; it is also used in tinning and soldering. The etching of cuts consists in the acid treatment of the areas of a metal (usually zinc) plate that are not protected by an acid-resistant layer; upon etching, these areas are deepened. Similar etching to create a desired surface profile is common in modern semiconductor technology and for the manufacture of integrated circuits (see alsoMICROELECTRONICS) and printed circuit boards in electronics. To produce the required circuit pattern, a chemically stable layer of a dielectric is applied to semiconductor crystals or printed circuit boards covered with copper, aluminum, or tin-nickel foil. The areas without this layer are etched—for example, to remove the metal layer.
The etching of semiconductor materials is an important operation in the manufacture of semiconductor devices and, in epitaxial technology, for the removal of impurities and oxides from the surfaces. Etching is used to remove damaged layers after mechanical working, for the controlled removal of material to obtain plates of given thickness with a finished surface, and for controlled alteration of surface properties. It is also used to create the required contour on the surface of a plate (for example, to etch out holes in preparing various types of alloy junction and surface-barrier transistors) and to limit the area of p-n junctions in finished diode and triode structures. Glass is etched to form a figure on its surface or to produce a matte surface, and wood is etched to impart to it a noncharacteristic appearance. Electrochemical etching is used successfully for metals and alloys such as tantalum, molybdenum, tungsten, and heat-resistant alloys, for which chemical etching is difficult, as well as for semiconductors. The advantages of electrochemical etching over chemical etching are the high surface purity obtained (no precipitate remains on the surface) and the extraordinary flexibility of control of the process.
Polished sections of crystalline materials, the surface of ingots and semifinished products, and the faces or cleavages of crystals are etched by various chemical reagents to reveal particular features of the chemical and phase composition and crystal structure. Such features may be observed with the unaided eye (mac-rostructure) or under a microscope (microstructure). This type of etching is used in scientific research and applied mineralogy (including the identification of ore minerals). In industry, it is used to monitor structure in the production of metals, alloys, semiconductors, and dielectrics. Crystal orientation is determined according to the symmetry of the etching figures on the faces. Etching figures have been used successfully, mainly in semiconductor technology, to reveal crystal defects such as small-angle and twinning boundaries, dislocations, and stacking faults.
G. V. INDENBAUM