mosaic

—mosaically, adv.

/moh zay"ik/, n., adj., v., mosaicked, mosaicking.

n.

1. a picture or decoration made of small, usually colored pieces of inlaid stone, glass, etc.

2. the process of producing such a picture or decoration.

3. something resembling such a picture or decoration in composition, esp. in being made up of diverse elements: a mosaic of borrowed ideas.

4. Also called aerial mosaic, photomosaic. an assembly of aerial photographs matched in such a way as to show a continuous photographic representation of an area (mosaic map).

5. Archit. (in an architectural plan) a system of patterns for differentiating the areas of a building or the like, sometimes consisting of purely arbitrary patterns used to separate areas according to function but often consisting of plans of flooring, reflected ceiling plans, overhead views of furnishings and equipment, or other items really included in the building or building plan.

6. Also called mosaic disease. Plant Pathol. any of several diseases of plants, characterized by mottled green or green and yellow areas on the leaves, caused by certain viruses.

7. Biol. an organism exhibiting mosaicism.

8. Television. a light-sensitive surface in a television camera tube, consisting of a thin mica sheet coated on one side with a large number of small globules of silver and cesium insulated from each other. The image to be televised is focused on this surface and the resulting charges on the globules are scanned by an electron beam.

adj.

9. pertaining to, resembling, or used for making a mosaic or mosaic work: a mosaic tile.

10. composed of a combination of diverse elements.

v.t.

11. to make a mosaic of or from.

12. to decorate with mosaic.

[1350-1400; ME < MF mosaïque < It mosaico < ML musaicum, re-formation of LL musivum (opus), L museum, musaeum mosaic work (quantity of u uncert.), of obscure orig.; variants may show an assumed relationship with Gk mouseîon shrine of the Muses, MUSEUM, by analogy with archi(v)um (see ARCHIVE), though classical Gk word is not attested in sense "mosaic"]

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Surface decoration of small coloured components

such as stone, glass, tile, or shell

closely set into an adhesive ground.

Mosaic pieces, or tesserae, are usually small squares, triangles, or other regular shapes. Mosaics cannot create the variations of light and shadow that paintings can, but glass tesserae can achieve a greater brilliance, especially those to which gold and silver foil have been applied. This technique was responsible for the great shimmering mosaics of the Byzantine period. The earliest known mosaics date from the 8th century BC and were made of pebbles, a technique refined by the Greeks in the 5th century. The Romans used mosaics widely, particularly for floors. Pre-Columbian Americans favoured mosaics of garnet, turquoise, and mother-of-pearl, which usually encrusted shields, masks, and cult statues.

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▪ art

Introduction

      in art, decoration of a surface with designs made up of closely set, usually variously coloured, small pieces of material such as stone, mineral, glass, tile, or shell. Unlike inlay, in which the pieces to be applied are set into a surface that has been hollowed out to receive the design, mosaic pieces are applied onto a surface that has been prepared with an adhesive. Mosaic also differs from inlay in the size of its components. Mosaic pieces are anonymous fractions of the design and rarely have the dimensions of pieces for intarsia work (fitted inlay usually of wood), whose function is often the rendering of a whole portion of a figure or pattern. Once disassembled, a mosaic cannot be reassembled on the basis of the form of its individual pieces.

      Technical insight is the key to both the creation and the appreciation of mosaic, and the technical aspects of the art require special emphasis. There are also significant stylistic, religious, and cultural aspects of mosaic, which has played an important role in Western art and has appeared in other cultures. Although mosaic is an art form that appears in widely separated places and at different times in history, in only one place—Byzantium—and at one time—4th to 14th centuries—did it rise to become the leading pictorial art.

Principles of design

      Between mosaic and painting, the art with which it has most in common, there has been a reciprocal influence of varying intensity. In colour and style the earliest known Greek figurative mosaics with representational motifs, which date from the end of the 5th century BC, resemble contemporary vase painting, especially in their outline drawing and use of very dark backgrounds. The mosaics of the 4th century tended to copy the style of wall paintings (mural), as is seen in the introduction of a strip of ground below the figures, of shading, and of other manifestations of a preoccupation with pictorial space. In late Hellenistic times there evolved a type of mosaic whose colour gradations and delicate shading techniques suggest an attempt at exact reproduction of qualities typical of the art of painting.

      In Roman (ancient Rome) imperial times, however, an important change occurred when mosaic gradually developed its own aesthetic laws. Still basically a medium used for floors (floor covering), its new rules of composition were governed by a conception of perspective and choice of viewpoint different from those of wall decoration. Equally important was a simplification of form brought about by the demand for more expeditious production methods. In the same period, the increasing use of more strongly coloured materials also stimulated the growing autonomy of mosaic from painting. As a means of covering walls and vaults, mosaic finally realized its full potentialities for striking and suggestive distance effects, which surpass those of painting.

      The general trend towards stylization—that is, reduction to two-dimensionality—in late antique Roman painting (3rd and 4th centuries AD) may have been stimulated by experimentation with colour in mosaic and particularly by the elimination of many middle tones for the sake of greater brilliance. The central role played at that time by mosaic in church decoration, for which it is particularly well suited, encourages the assumption that the roles had shifted and painting had come under its influence. The strong, sinuous outlines and the absence of shading that came to characterize painting during certain periods of Byzantine and western European art of the Middle Ages may have originated in mosaic technique and use of materials. It is notable, however, that from the Renaissance to the 20th century, mosaic was again wholly dependent on painting and its particular forms of illusionism.

      In modern mosaic practice, the main tendency is to build on the unique and inimitable qualities of the medium. Although not a few of the works created in the 20th century reveal the influence of painting, figurative or abstract, the art has gone a long way towards self-realization. By and large the modern mosaic maker shares with his medieval predecessor the conviction that there are functions to which the materials of mosaic lend themselves with particular appropriateness.

Materials

      In antiquity, mosaics first were made of uncut pebbles of uniform size. The Greeks, who elevated the pebble mosaic to an art of great refinement, also invented the so-called tessera technique. Tesserae (Latin for “cubes” or “dice”) are pieces that have been cut to a triangular, square, or other regular shape so that they will fit closely into the grid of cubes that make up the mosaic surface. The invention of tesserae must have been motivated by a desire to obtain densely set mosaic pictures which could match, in pavements, the splendour of contemporary achievements in painting.

      Tesserae vary considerably in size. The finest mosaics of antiquity were made of tesserae cut from glass threads or splinters of stone; ordinary floor decorations consisted of cubes about one centimetre square. Medieval works often display a differentiation in tessera size based on function: areas requiring a wealth of details, faces and hands, for instance, are sometimes set with tesserae smaller than average, while dress and jewelery are occasionally set with very large, single pieces.

      As long as mosaic was a technique for the making of floors, the main requisite of its materials, besides their colour, was their resistance to wear.

Stone

      Stone, therefore, was long dominant, and throughout antiquity the natural colours of stone provided the basic range of tints at the artist's disposal; they put their mark not only on the earliest Greek works but continued to determine colour schemes far into Roman times. Stone continued to be used in Christian monumental decorations but on a more limited scale and for special effects. In Byzantine mosaics, faces, hands and feet, for example, were set with stone, while cubes of marble, often of coarse crystals, were used to depict woollen garments. Stone was also used for background details (rocks, buildings), probably to bring about particular illusions. Though marble and limestone were ordinarily preferred, in a period when Roman mosaic cultivated a black and white technique, black basalt was widely employed. Marble cubes painted red, probably to substitute for red glass, have been found in many Byzantine mosaics, in 9th-century works at Istanbul, for example.

      Because its granular, nonpolished surface is often preferred to the hard brilliance of other materials, stone is also widely used in modern mosaics. At the University of Mexico in Mexico City, for example, the mosaics covering the exterior of the library by Juan O'Gorman (1951–53) and the exterior of the stadium by Diego Rivera (1957) are made with natural stone.

Glass

      Glass, which first appeared among the materials of mosaic in the Hellenistic (Hellenistic Age) period (3rd–1st century BC), brought unlimited colour possibilities to the art. In floors, however, it had to be used sparingly because of its brittleness. In floors, glass tesserae were used for the strongest hues of red, green, and blue, while softer tints were rendered with coloured stone. With the development of wall mosaic, glass largely took over the functions of stone, producing tints of unsurpassed intensity and leading to a continuing search for new coloristic effects.

      With little knowledge of the laws of optics but with immense practical experience, mosaic makers of the Early Christian (Christianity) period gave the art a completely new direction with the exploitation of gold (goldwork) and silver glass tesserae. Like a mirror, the glass from which this kind of tesserae was made had a metal foil applied or, better, encased in it. The metal was gold leaf or, for the “silver,” probably tin. These pieces of mirror glass gave golden or white reflections of high intensity and could be used to depict objects of precious metal or to heighten the effect of other colours; but, above all, it was used as a means of rendering the light emanating from God.

      Gold tesserae were first used by the Romans, in both floor and vault decoration of late antiquity. Initially, their role was simply to give a golden effect. Gold tesserae, for example, were employed to depict a golden wreath in a floor mosaic at Antioch (c. AD 300) and gold vessels in some of the vault mosaics in Sta. Costanza in Rome. Later, when this use of gold for imitation purposes had become more refined, some spectacular effects were produced in the depiction of garments. The Good Shepherd in the Mausoleum of Galla Placidia at Ravenna (c. AD 450) is dressed in golden robes of densely set gold cubes shaded with stripes of light-yellow tesserae. The female saints in S. Apollinare Nuovo (c. AD 550–570) in the same town wear costumes set with green glass cubes among which appear both patterns and large fields of gold tesserae, producing a striking similarity to rich silk brocade. Silver was used in a similar way. Christ scenes in S. Apollinare Nuovo (AD 500–526) employ silver tesserae in the drawn sword of Peter in the betrayal, no doubt an imitation of steel. Silver tesserae are also found in the silver jug and basin in the scene of Pilate washing his hands.

      Gold cubes were distributed among the ordinary tesserae to add to the shimmer of light in ornaments and background details. To avoid an uneven gleam in the surface, the mirror effect was often moderated by setting the gold tesserae in reverse, so that the visible part of the cube is the side with the thickest sheet of glass covering the gold leaf. In the now-lost mosaics of the Church of the Dormition in Nicaea, a scholar observed another exquisite effect, which he called dark gold, created by cubes from which some of the gold leaf had been chipped off, for example, in the frontal part of Mary's golden footstool (7th or 8th century AD).

      An early instance of the use of gold for depicting light emanating from God is in a representation of Christ-Helios (Christ as the Sun God) in a 3rd-century mausoleum under St. Peter's at Rome. Here, a few gold tesserae are seen in the rays coming from Christ's head. The halo of gold, a feature so common in Christian art that religious pictures without it can hardly be imagined, developed in mosaic art in the 4th century AD. The gold background, signifying divine light, probably originated in Roman mosaic art, but the first preserved instances date from the advanced 4th century. The cupola mosaic of Áyios Geórgios at Thessaloníki (c. 400), for example, has a background of gold. In Italian mosaics of the 5th century, other types of background, such as a dark-blue ground or a more naturalistic landscape setting, were dominant. Only at the beginning of the 6th century did the gold background become the rule.

      In addition to this massive predilection for gold, the Christian East began to use silver to depict the symbolic light emanating from Christ. First, it was used for the entire disc of his halo, later only for the cross arms. The archangels were the only figures besides Christ for whom the silver halo was used. The light of God, appearing as rays from above in scenes of the Annunciation, Nativity, Baptism, and Transfiguration, was also depicted with silver tesserae. Finally, silver and gold were used together in Byzantine representations of the infant Jesus whose golden robes are highlighted with silver cubes (the apse and south vestibule of Hagia Sophia, Istanbul; both 9th century).

Other materials

      In Christian mosaics, tesserae of mother-of- pearl or coarse-grained marble cut to round or oblong shapes were used to depict pearl. Though pieces of semiprecious stones were among the mosaic materials of antiquity, their use was rarely dictated by the wish for particular sumptuous effects. Reduced to common tessera size, bits of this strongly coloured material served as part of the general colour scheme of the mosaic pictures. Objects like those of the pre-Columbian American Indian cultures, in which, because of its exquisite materials, such as turquoise and garnet, mosaic attained the status of jewelry have not been found in Western art.

      Among the materials that have played and continued to play a role in the production of mosaic, ceramic (pottery) is the most versatile. terra-cotta “threads” were used in Greek mosaics as contours, and tesserae of the same material were frequently used by the Byzantines for the depiction of red objects and garments. Today, glazed or unglazed ceramic is used and is one of the strongest competitors with glass and stone. Ceramic tesserae are cut from tiles or, like much modern glass mosaic material such as pressed glass, come prefabricated. Prefabricated tesserae have the advantage of a very uniform and smooth surface which harmonizes with glass, steel, and other new building materials.

Techniques

      The most commonly used adhesive for mosaics was mortar, the function of which in the 20th century has been largely taken over by modern, tougher kinds of cements or glue. In Roman floors, two to three layers of mortar preceded the setting bed that was to carry a tesserae facing. The first layer rested on a thick foundation of stone that prevented settling of the mortar bed and the formation of cracks. For wall mosaics the preparation was equally painstaking, and in many cases an application of a waterproofing of resin or tar preceded the laying of the mortar. There then followed two layers of coarse, roughened mortar, the stability of which was often improved by large nails that had been driven into the joints of the wall before the work of laying started. A third and final layer was of fine consistency and frequently, like the mortar for floor mosaics, contained powdered marble and binding elements such as pounded brick.

      As in fresco painting (technique of using water-suspended pigments in a moist plaster surface), the setting bed was applied in patches never larger than were needed for one day's work. In a frescoed surface, the breaks between the different stages of the work can easily be detected; they are harder to discover in mosaic.

      Numerous underpaintings discovered in wall mosaics indicate that sketches (sketch), often detailed and with the main colours suggested, were executed on the setting bed to serve as guides for the disposition of the tesserae. Similar procedures are thought to have been part of the technique of floor mosaic. In church mosaics, rough preliminary sketches have been found on layers underneath the setting bed and, in a few instances, even on the brick wall itself. This kind of preparatory sketch, for which there are parallels in wall painting, suggests that the artist was trying out the overall scheme of the decoration before making a more detailed sketch on the setting bed.

      Instead of laying the tesserae one by one directly onto the mortar, another method was sometimes used. In Pompeii many of the so-called emblēmata (emblema) (central panels of floors), which were made up of smaller than average tesserae and were often of very high artistic quality, appear to have been preset on trays of stone or terra-cotta which were then embedded in the mortar of the floor. The surrounding mosaic area was then set according to the ordinary, direct method. Although the direct method was used for wall mosaics during the Middle Ages, there are signs in at least one medieval monument of a partial use of the prefabrication—or “indirect”—method: in the cupola mosaic of the church of Áyios Geórgios, Thessaloníki (c. 400), the heads of the saints seem to have been inserted in the mortar in one piece. The indirect method is the one most used in the 20th century. In the workshop, the mosaic is first set in reverse with glue on paper or cloth and then applied to the floor or wall. The technique permits preassembling of mosaics intended even for curved surfaces, cupolas, or apses. It has been hypothesized that behind the enormous output of floor mosaics in the Roman era lay similar production methods which had developed out of the tray procedure described above. The introduction of wall mosaics led to experimentation with the spacing and angling of tesserae. The solidity of floor mosaics depended on a close-set texture, but in wall mosaics, in which the element of wear was no longer relevant, the organization of the surface could become looser. For several centuries, a very wide spacing of the tesserae was cultivated, and the placing of cubes at irregular angles was regarded as important to the over-all effect of wall mosaics. These tendencies reached the extreme in the 7th and 8th centuries, in mosaics of the chapel of S. Venanzio in the Lateran Baptistery, Rome, and in the fragments of the decoration of Pope John VII (AD 705–707) in the old St. Peter's (Old Saint Peter's Basilica) in the Vatican. Later periods preferred a somewhat closer setting, but the irregular surface continued to be in fashion for most of the Middle Ages.

      The tilting of tesserae became an art in itself. In 6th-century Byzantine mosaics, there evolved a new technique whereby gold and silver tesserae were set at extremely sharp angles to enhance reflection. By pointing their mirror ends downward in the direction of the onlooker it was possible to secure maximum light effect. In Hagia Sophia at Istanbul, the enormous gold areas in the wall mosaics of the emperor Justinian are set with cubes tilted this way. In one particularly dark corner, the tesserae are not only tilted downward but are also turned slightly sideways to catch the light from a nearby window. A similar technique, based on a high degree of tilting of the gold tesserae in unlit areas, can be observed in the mosaics of the Dome of the Rock in Jerusalem (c. AD 690).

      Haloes set with tilted cubes that bring out the circle of light surrounding the heads of holy figures became common in Byzantine mosaics of the 6th to 7th centuries, as is seen in the mosaic panels dating from this period in the church of Áyios Dhimítrios, Thessaloníki. Striking examples of such haloes are also found among mosaics that were put up in Hagia Sophia in Istanbul in the 9th century, above all in a panel with the kneeling emperor (Leo VI?).

      Effects such as those described above are unthinkable without the accumulated experience of the craftsman-artist. In the 20th century, mosaic increasingly has become an art divided between the inventor who furnishes the design and the worker who executes it. It may be that the dry character of many modern mosaics can be ascribed to the fact that the artist no longer puts his thumb on every tessera.

Periods and centres of activity

 Among the cultures of the ancient Near East there is one remarkable occurrence of a mosaic-like technique: the exteriors of some large architectural (architecture) structures, dating from the 3rd millennium BC, at Uruk ( Erech) in Mesopotamia (art and architecture, Mesopotamian), are decorated with long terra-cotta cones imbedded in the wall surface (see photograph—>). The blunt, outer ends of the cones, coloured in red, black, and white, form patterns consisting of zigzag lines, lozenges, and other geometrical motifs. This revetment was decorative as well as functional, for the cones shielded the core of sun-dried bricks from rain and wind. The technique, however, died out and seems to have had no influence on the later development of mosaic.

      In western Asia Minor (art and architecture, Anatolian) are preserved the earliest examples of the surface-covering technique that lead to mosaic in the present sense of the word. In the town of Gordium near modern Ankara in Turkey, houses have been uncovered with floors made of pebbles set in a primitive mortar. In some of these floors (dated to the 8th century BC), rows of light pebbles form awkward geometrical figures against a background of darker stones. These rudimentary elements of decoration introduced into a crude form of pavement laying spurred artistic imagination and set in motion a process that was to bring spectacular results.

Ancient Greek and Hellenistic mosaics

      Three main phases can be determined in the development of mosaic art in antiquity. The first, chiefly a Greek matter, involved the gradual perfecting of the pebble (pebble mosaic) medium. The second, which saw the invention and spreading of the tessera technique, took place partly in the Hellenistic Greek world and partly on Roman soil. The third, largely a Roman phenomenon, was characterized by the popularization of mosaic and the application of the medium to new functions. By a process of diffusion, the taste in floor decoration documented at Gordion spread through the Greek-speaking world of the Mediterranean. Its first full flourishing seems to have occurred in late Classical times. Pebble mosaics are found as far west as Sicily (Motya, Morgantina) and, in the east, in the Greek colonies on the Crimea (Cherson). They are preserved in large number at only two sites, Olinthos (Olynthus) and Pella, in Macedonian northern Greece.

      In the town of Olinthos there are floor mosaics, with elaborate figures and complicated patterns, which were part of the new city culture that developed in the 5th century BC. The Olinthos mosaics also reveal that picture making with light and dark pebbles had by then evolved into an intricate art. Against a ground set with black or blue-black stones stand figures or patterns set with white or slightly tinted ones. Pebble size had become fairly uniform, with diameters from one to two centimetres, but particularly intricate areas, like faces, are set with smaller stones. Very small black pebbles serve as outlines. Although the mortar between them is visible, the pebbles are set close enough so that the pictures appear with regular, not too broken outlines and with some emphasis on detail.

 Floors in houses at Pella, dating from the 4th century BC, demonstrate a significant later development of the pebble technique (see photograph—>). Floor mosaics then openly vied with wall painting in the rendering of space and realistic detail. This was made possible by the introduction of new materials that eliminated the shortcomings of the ordinary pebble medium. Among the basic changes was an increase in the range of colours. When the demand for particular tints could not be met with pebbles of natural colours, “artificial pebbles” were made and are found in several of the floors at Pella. These “pebbles” have been painted in the required tones—mostly strong green and red—and, to protect the film of paint, have a depression sunk in the middle. The new trend also called for smaller pebbles to permit pictures to be set more closely. To obtain precise delineation of limbs and features, outlines made not with pebbles but with long strips of terra-cotta or lead wire were employed. Pictures made in this technique reflect a taste for heroic hunt scenes and fights with wild animals, themes inspired from court art glorifying the ruler.

      The next innovation came at the end of the 4th or the beginning of the 3rd century BC, when the introduction of new principles led to the abandonment of the pebble technique. Cut mosaic pieces permitted the nearly complete elimination of the disturbing effects of visible mortar patches, and new materials, above all glass, offered a vast new range of colours. The acceptance of the new methods and materials seems, however, to have come about slowly. In Alexandria (Greco-Roman Museum) there is a mosaic (depicting Erotes fighting a stag and, in the outer border, a frieze of animals) in which cut, triangular tesserae are used together with both pebbles and lead wire. In somewhat later Alexandrian mosaics made with tesserae (late 3rd/early 2nd century BC) lead threads are still in use; for example, in a panel signed by the artist Sophilos and depicting a personification of Alexandria, that is the earliest known example of miniature mosaic work (called opus vermiculatum, meaning “wormlike work” because of the close-set, undulating rows of small tesserae).

       Pergamum, another centre of the Hellenistic world, was particularly famous for its school of mosaics. According to the ancient Roman historian Pliny the Younger, Sosos, one of the most renowned mosaic artists of antiquity, worked in this city. None of his works survives but, thanks to Roman copies, the intentions that underlay his art can be judged. Pliny listed as his most celebrated works a representation of drinking doves and a clever imitation of the “unswept floor” of a banquet room (asarōtos oikos). The copies tell of Sosos' phenomenal ability to create trompe l'oeil (“fool-the-eye”) effects through a shading and colouring that seems to bring the objects out in full plasticity on the ground on which they are depicted. To call the work merely an imitation of painting may be incorrect. The intense colours and the smooth texture permitted by the new setting technique paved the way for illusionistic effects that went beyond those achieved by painting.

Roman mosaics

   Eager to adopt the artistic culture of the Hellenized eastern Mediterranean, the Romans introduced mosaic in this exquisite form in both their domestic architecture and their places of worship. Pompeii has yielded a host of opus vermiculatum works datable to the 2nd/1st century BC. Among these the most famous is the Battle of Issus (Issus, Battle of), found in the Casa del Fauno in 1831 (see photograph—>). This is the largest of all known works, measuring about 11.22 by 19.42 feet (3.42 by 5.92 metres), in the miniature mosaic technique. This mosaic (which probably copies a work of painting, perhaps a famous picture by Philoxenus of Eretria) and other Pompeiian panels of similar quality are supposed to have been executed by Greek artists, who carried on in the tradition established at Alexandria and Pergamum.

      The Romans transformed mosaic from an exclusive art to a common decorative medium. Some of the earliest examples of this new type of floor are in the late republican (2nd century BC) houses at Delos. For rooms of secondary importance and often for floors surrounding the finely designed and executed central emblēmata (a featured picture or ornamental motif) in the most important rooms, the Romans developed a simpler, less artistic kind of mosaic. The floors are set with fairly large tesserae with a limited range of colours, some tending toward monochrome (black-and-white). The decorative designs and motifs are also simple and uncomplicated.

 This new trend in mosaic floors (floor covering) was probably stimulated by new and functional ways of thinking about the role of floors in architecture. To the practical Romans it may have seemed illogical that floors destined for rough wear should bear delicate pictures. Moreover, the demand for large-scale mosaic making brought about by the colossal urban expansion in the 1st century AD made the development of quicker and simpler techniques imperative. The aim of the Romans seems to have been to create a style, technique, and form of composition that would be simple and functional. Competition with painting in illusionistic and coloristic refinement was therefore abandoned; emblēmata gave way to decorative elements distributed over the floor in one large overall pattern or to figure compositions taking the full floor plane; and polychrome gave way to monochrome mosaics (which may have been easier to produce). Enormous floors in the baths and in the courtyards of warehouses (1st to 3rd century AD) at Ostia, Rome's port at the mouth of the Tiber, are the best preserved examples of the monochrome style (see photograph—>).

      The expressionist Roman style, which flourished in Italy, penetrated into the former Greek cities in the eastern part of the empire, but polychromy and types of composition based on the framed picture persisted with especial tenacity due to strong local Hellenistic traditions. A splendid series of emblēmata (2nd century) with mythological representations, allegories, and scenes from the theatre have been uncovered at Antioch in southern Turkey. They prove the existence of a school there of mosaicists of particular brilliance. Recent research has pointed to the African provinces as the site of another, highly active school with a taste for larger, dramatic compositions. Influence from these areas may have been responsible for the renewed opulence, represented by a vivid polychrome pictorial mosaic, which reappeared in Roman art in late antiquity. Outstanding examples of this renewal are the mosaics in the Roman villa of Casale (c. AD 300) near Piazza Armerina, Sicily. The mosaic decoration of this vast palace complex culminates in the gallery of the Large Hunt, which contains a scene of animal hunting and fighting covering an area of 3,200 square feet (300 square metres).

 It is generally agreed that in the course of the 3rd century the status of mosaic was radically altered. Already in Hellenistic times the medium had been employed for other ends than floor covering and had become part of the embellishment of the fantastic garden architecture of which the rulers of the period seem to have been particularly fond. Reflections of this tradition in the 1st century AD are the mosaic-covered fountains in the mansions at Pompeii and Herculaneum and mosaic panels and niches in rustic banquet halls and artificial grottoes at The Golden House of Nero in Rome and his villa at Anzio. Mosaic fragments and imprints of tesserae in the vaults of baths and buildings of similar size demonstrate that mosaic gradually was introduced into new fields. Equally important is the evidence that mosaic was used to depict sacred images. On some of the monochrome floors at Ostia are scenes pertaining to animal sacrifice and to the cult of the dead. Three monuments of the 3rd century inform of another new practice introduced at this time, that of putting mosaic pictures of religious importance on walls: a niche mosaic with the god Silvanus from a temple of Mithra at Ostia; a Christian wall and vault mosaic depicting Christ as Helios, the Sun God, in a mausoleum under St. Peter's, Rome; and a decoration, now lost but recorded in a 17th-century drawing, of a chapel for the Lupercalian worship at Rome. It has been pointed out by modern scholarship that the new role gradually assumed by mosaic must be related to the corresponding decline in interest in three-dimensional representation. The cultic mosaic took over the function of the cult statue, mosaic being that two-dimensional medium which was considered most capable of convincingly expressing religious ideas in visual form.

Early Christian mosaics

      Present-day insight into the crucial, early phase of this part of the history of mosaic is limited because of the loss of nearly everything that was made in the field during the first half of the 4th century. Nevertheless, as indicated above, it seems certain that wall mosaics had come into use in Roman art well before Emperor Constantine's edict of toleration of the Christian faith in AD 313. Considered to be among the earliest Christian wall mosaics in Rome are those in the church of Sta. Costanza built about AD 320–330 as a mausoleum for Constantine's daughter. The content of the pictures is almost completely Dionysiac and pagan, but a series of small format scenes from the Old and New Testaments were included among the non-Christian pictorial elements of the decoration. Obviously an independent Christian pictorial program for buildings of Sta. Costanza's size and complexity had not yet been developed; and, probably in lieu of that, a Dionysiac program had been chosen because its many allusions to the symbolism of wine lent themselves to a Christian interpretation.

      Other monuments of the 4th century bear similar marks of transition. Floor mosaics in the cathedral complex at Aquileia demonstrate that the church before and immediately after Constantine's edict of tolerance of the Christian faith in AD 313 adhered to the late antique tradition of placing religious pictures in pavements. In the earliest group of Aquileia mosaics (c. AD 300) objects and animals symbolize the Good Shepherd, while the later group (second decade of 4th century) contains scenes from the story of Jonah, symbolic animals, such as the deer and the lamb, and a representation of the bread and the wine. Before long, pictures of this character were banished from floors, and simpler and more general symbols took their place.

      The latest of the preserved transitional works, a decorated cupola in a mausoleum, possibly imperial, at Centcelles (now Constantí, Tarragona), Spain, seems to have been made not long after AD 350. This very fragmentary decoration has yielded important information about a stage of increasing mastery in the handling of the medium. The scenes from the Old and the New Testament are presented with greater self-confidence and occupy a full, broad zone in the lower part of the cupola. Yet, below it is a stag hunt, rich in symbolic content but adhering closely to the patterns of profane floor mosaics. Stone tesserae dominate in the lower zones, but glass cubes are found in large quantities in the upper. Glass, with its stronger colours, was doubtlessly concentrated in this area intentionally. The zenith of the cupola, weak in lighting and distant from the spectator, needed tesserae of strong reflecting power to make it possible to read its decoration.

      A series of large, in part well-preserved mosaics make it possible to follow the progress of the art in 5th-century Italy. Ravenna and Rome (ancient Rome) have several important works, while Naples and Milan have preserved enough to suggest that workshops of high artistic standard must have existed in many of the large cities of the peninsula. In these works, the tendency to clarify and even underline the content of religious pictures with the help of colour is brought to its full peak. The swing towards a greater employment of glass reached a point at which the mosaics are almost entirely made of this material. In what must be regarded as a late but vigorous revival of the painterly illusionism of antiquity, there is an audacious blending of colours. Among the high points of this trend are the flaming visages of angels in Sta. Maria Maggiore, Rome (c. AD 432–440) and the spiritualized physiognomies of St. Bartholomew and his fellow apostles in the Baptistery of the Orthodox, Ravenna (c. 450). But the designer's mastery and sophistication are nowhere more overwhelmingly illustrated than in the glowing interior of the so-called Mausoleum of Galla Placidia (c. 450) at Ravenna, with its blue star-filled mosaic dome, and in the decoration of the Naples Baptistery of S. Giovanni in Fonte (5th century), with its hypnotizing glimmer.

      A Christian language of pictures ( iconography) was now developed, and its grammar worked out. In cupolas, the centre tended to be reserved for depictions of Christ or the cross. In apses there was a trend toward static and symbolical representation of holy figures and a reduction of detail. On the walls of the nave of basilicas were scenes from the Old or the New Testament or both. The largely intact decoration of the church of Sta. Maria Maggiore, Rome, throws some light on the principles involved.

      Old Testament scenes are distributed on the side walls of the nave in panels measuring about six by six feet (1.9 by 1.9 metres). There is one panel below each of the basilica's large windows. The pilasters (columns projecting shallowly from the surface of the wall) between the windows (restored but repeating the original disposition) serve as outer frames for these panels. Before the restoration of the church in the 16th century there were also inner frames, made of stucco; in addition, each panel was adorned with a small pediment (triangular gable) of the same material and thus appeared as if enshrined by a small aedicula (a pedimented niche). The classical rules governing the relation between the architecture of a building and its decoration may be expected to leave their mark on Christian mosaic art for a long time.

Byzantine (Byzantine art) mosaics

Early Byzantine mosaics

      Mosaics made in Ravenna for the Ostrogoth king Theodoric (AD 493–526) are the first full manifestations of Byzantine art in the West. As seen in two of the foremost works from his time, the Baptistery of the Arians and the church of S. Apollinare Nuovo, the gold background now dominates. Accompanying it was silver, a novelty among the mosaics of Italy. In S. Apollinare Nuovo, the faces and hands in several of the Christ scenes are set not with glass tesserae but with cubes of stone. Stylistically, these mosaics are characterized by more static figures and less depth and plasticity than in those of the 5th century.

      Another remarkable element is the movement, now fully developed, toward an integration of architecture and mosaic decoration. This is most clearly seen in the basilica. In the church of S. Apollinare Nuovo, the mosaics are no longer inserted panels but form a continuous “skin” that covers every inch of the wall. The size of the windows and even their number have been reduced, apparently to provide more wall space for pictures. Figures have grown in size, to match the dimensions of architectural components, and they seem to have taken the place of pilasters in the articulation of the room. This trend is given truly monumental expression in the choir of the church of S. Vitale at Ravenna, dating from c. AD 526–548. A profusion of decorative elements is spread like tapestry over the walls and vault, the panels of the emperor Justinian and his consort Theodora near the apse embodying the new spirit in their colour-laden pageantry.

      In the East, the circular church of Áyios Geórgios at Thessaloníki, Greece, shows Byzantine mosaic at its earliest flourishing (c. AD 400). Its partly preserved mosaics display a disposition related to that of the Baptistery of the Orthodox at Ravenna, with a lower zone containing Paradisiac architecture; above this a zone with standing and walking figures and in the centre of the cupola a medallion with a figure of Christ. A uniform gold background dominates the two lower zones, at a time well before it had come into general use in the West. Silver is found in profusion, used for the background in the central medallion as well as a means to enhance the radiation of light from all parts of the mosaic. In the figures of saints the material for faces and hands is chiefly natural stone, its gentle gradations contrasting spectacularly with the violent juxtapositions of coloured glass tesserae of the hair and the garments.

      Effects of this kind, which are the hallmark of Byzantine mosaic technique, seem to derive from intentions wholly dissimilar to those which had determined the development of early Christian mosaic art in the West, where the illusionism of Greco-Roman art persisted for a long time. In the great Ravenna mosaics of the 5th century, pictures illustrating the narrative of the Bible or expounding the dogmas of religion were still done in the painterly style of Roman mosaics and wall painting. During the same period, mosaic art of the Eastern Empire, having abandoned conventional illustration, was boldly exploring the way that lay open, in mosaic art, toward a new kind of imagery.

      In the mosaics of the 6th century are found the earliest refinement introduced by the Byzantines to enhance the brilliance of gold tesserae. This refinement, already described, involved setting gold cubes at oblique angles to direct their reflections toward the viewer. Used in haloes, the tesserae, obliquely set, convey to the holy figures a miraculous aura of light. The visages of the saints, with their dull stone surfaces and hues reminiscent of actual human skin, add a touch of mysterious reality to this theatre of effects.

      Splendid mosaics from many parts of the eastern Mediterranean testify to the continuous cultivation and improvement of these effects. In the city of Thessaloníki the mosaics in the churches of Hosios David (5th century AD) and Áyios Dhimítrios (6th and 7th centuries) exemplify the trend, which is also expressed in apse decorations preserved at Cyprus (church of the Panagia Angeloktistós, at Kiti, and of the Panayía Kanakaria near Lythrangome; both 6th century) and in the Monastery of St. Catherine, Sinai Desert, founded by Justinian.

      Apart from the gold ground, which had considerable impact, the technical subtleties essential to these mosaics met very little response outside Byzantium. When Byzantine artisans operated in foreign territory, they brought their particular techniques with them. Again and again the impact of this tradition was felt in the West, though, at its purest, mostly as short-lived episodes. To judge from a few surviving fragments, mosaics executed under Pope John VII (AD 705–707) in a chapel in St. Peter's, Rome, might have been the work of artisans summoned from Byzantium. Technical and stylistical features demonstrate that the mosaics executed under the earliest Muslim rulers, in the Dome of the Rock at Jerusalem (c. AD 690) and in the Great Mosque at Damascus (c. AD 715), are certainly the work of specialists called from Byzantium. Sources testify that even the mosaics in the mosque at Córdoba, Spain (AD 965), were made by Greek craftsmen.

      The floor mosaics in the great palace of the Byzantine emperors at Istanbul—with their pastoral scenes, fights with wild animals, and figure groups taken from pagan mythology—testify to an undercurrent of classical taste in Constantinople. The date, which according to archaeological evidence must be placed as late as around the year AD 600, demonstrates the tenacity of that taste in the midst of the Christian milieu of the Byzantine metropolis.

Middle Byzantine mosaics

      Scholars have been concerned to discover how Iconoclasm (Iconoclastic Controversy), the dispute concerning images during the 8th and 9th centuries, may have influenced the course of Byzantine art. In some respects, at least, mosaic reflects very little change. The main source of knowledge about the state of mosaic in the time shortly after the end of Iconoclasm is Hagia Sophia at Istanbul. Parts of the redecoration that the church underwent in the last half of the 9th century have been uncovered in recent times. In their colour and technique these show a continuation of the early Byzantine tradition: the preference for rather strong, clear tints, and the effects created by such techniques as the tilting of tesserae and the turning of gold cubes. The preoccupation with light seems stronger than ever: in badly lit places in the vestibule and gallery, the gold ground displays a high percentage of silver cubes among the gold ones to add to the sparkle. Stylistically, new ground had been broken. Particularly in faces, the tesserae are set in wavy lines which break up the modelling in bandlike configurations. Linearism (the expression of form in terms of line rather than colour and tone) had taken a great step forward.

      In the arrangement and distribution of pictures new features are visible. In the apse of Hagia Sophia, the Virgin with the Child sits surrounded by a vast expanse of gold. She is one of the first of a family of similar majestic madonnas, the most striking of which is in the Cathedral of Torcello near Venice (12th century). The tendency to depict icon-like, motionless mosaic figures isolated on a gold background has pre-Iconoclastic precedents, but from the 9th century onward it became a leading decorative principle.

      Nineteenth-century drawings show that the decoration of Hagia Sophia also included comprehensive series of saints. Of these saints, which stood in rows on the nave walls above the galleries, only a few have survived. According to the drawings, those of the middle zone represented prophets, those of the lower, holy bishops. Higher up there may have been a guard of angels and in the centre of the cupola, probably a mosaic of Christ. The disposition of the pictures, in other words, may have corresponded to that which at this time was being tried out especially for the new church architecture and which was to become the accepted system of decoration in the middle Byzantine churches.

      The monastery church at Daphni, near Athens, contains one of the best preserved decorations of this type. The building belongs to a category of central-plan structures that had come into fashion and was to dominate for centuries both in Byzantium and in other areas under the influence of the Orthodox Church. The interior of the church at Daphni displays a layout which, compared with the wealth of detail of the early Christian period, appears single-minded and concentrated. In the centre of the dome is a medallion containing a colossal bust of Christ as Pantokrator, the All-Ruler. In the lowest part of the dome, separated from the medallion by a broad zone of gold, stand prophets with their scrolls. Further down, there may originally have been medallions with portraits of the Evangelists. In the four arches that carry the drum of the cupola are scenes from the life of Christ which, with eight more Christological scenes in the transepts, formed a cycle devoted to the central feasts of the church. The Virgin is represented in the apse, her guard of archangels on the side walls of the sanctuary. About thirty saints, depicted either as busts or as full-length figures, fill the remaining wall space. In the vestibules are more scenes from the life of Christ and the remains of a cycle devoted to the life of the Virgin. Golden frames with floral ornaments surround the panels, and gold once covered every inch of wall between them.

      The ensemble represents a visualization of the Christian cosmos, its effect created by an intricately conceived interplay of pictures and architecture. The worshipper who moves within this golden shell finds its world of pictures thoroughly involved with space. Space in fact fuses the decoration into one giant image, in which the ruler, hailed by the prophets surrounding him, presides in his sphere above the host of saints that people the lower part of the room.

      Subtle spatial devices animate the individual pictures; figures of saints, their two-dimensionality emphasized by their outlines, appear in niches sunk in the wall or lean forward in the interior curves of arches. The 20th-century Austrian scholar Otto Demus, in studies on the aesthetics of middle Byzantine mosaic art, has coined the term space icons for this kind of imagery, in which the forms of architecture collaborate to make the solemnly stylized figures appear with unexpected tactility. As shown by Demus, the spatial element contributes to the narrative scenes also. In the four arches, for example, the hollow plane on which the scenes from the life of Christ unfold adds a dimension of spatial realism to the total image. This is most clearly to be observed in the Annunciation scene, where Mary and the Angel face each other across a stretch of real space. The figures share or are made to appear to share the room with the beholder.

      The “classical system,” as this close interrelation of architecture and mosaic has been called, was probably perfected in the course of the 9th to 10th centuries, but the earliest fully preserved examples are from the 11th to 12th. Besides Daphni, Greece owns two more monuments of this kind, the monastery church of Hosios Loukas in Phocis and the Nea Moni on Chios (both 11th century). Similar churches are found in such widely distant places as Kiev (Hagia Sophia, 11th century) and Palermo (Martorana, c. 1150), both the products of strong Byzantine influence. The system, however, is not identical in any of these. The churches belong to the same general type, but their plans and elevations vary and thus require variations in this disposition of pictures as well.

      The classical system with its emphasis on totality may have led to the gradual toning down of the many splendid effects of the earlier tradition for the sake of the equilibrium and clarity of the whole. At Daphni, for example, the rich, tapestry-like character of earlier mosaic has given way to a controlled, less sparkling range of tints. The reds and yellows are restricted, their function in the overall scheme taken over by the gold of the background. Sombre, often hard blues, greens, and violets are preferred to the lighter ones. Compared with the Hosios Loukas and the Nea Moni mosaics, which retain more of the older colour scheme (the latter almost to the point of brutality), the Daphni mosaics appear cool and intellectual, an impression further conveyed by their elegant style. Actually they belong to a new phase of Byzantine art which took its name from the dynasty of the Comnenus (Comnenus family) (AD 1081–1185). This style appears at its most refined in Hagia Sophia, Istanbul, in a panel depicting the Virgin flanked by the emperor John Comnenus II and his wife Irene. The practice of tilting the gold tesserae also seems to have been abandoned, for it is not found at Daphni nor in any of the mosaics that are examples of the fully developed classical system. Silver was reduced to the single role of depicting the light emanating from God and Christ (Christianity). This drying out of the effects of light and colour was partly compensated for by a perfectionist setting and spacing of the tesserae.

Late Byzantine mosaics

      The phenomenon called the Palaeologian (Palaeologus family) Renaissance (from the dynasty of the Palaeologians, 1261–1453) led to a renewal of Byzantine mosaic art. The stylistic innovations that made themselves felt both in painting and mosaics of the late 13th and beginning 14th century bear witness to one of the most startling changes that ever took place within the framework of Byzantine culture. Bred by a vital humanism, which penetrated westward and laid the foundations for the Italian Renaissance, painting showed a predilection for perspective and three-dimensionalism. A peculiar vivacity invaded religious art, together with a sense of pathos and of the tragic. The results, as expressed in mosaics, were extraordinary.

      To respond to the new trend, mosaicists recast their technique. The tessera size generally became smaller than it had been in earlier epochs; and contours lost their rigidity, became thinner, and were occasionally abolished. Colour was reintroduced in a manner that gives the Palaeologian works a striking likeness to the mosaics of the Early Christian period, which, one must suppose, in many cases served the artists as models. An interest in the optical effects of gold apparently returned but rarely, it seems, in the form of the tilting technique. On flat walls, the gold ground was sometimes set in a shell pattern, probably to enhance the play of light on the surface and to avoid a too-uniform brilliance. For domes, a densely ribbed form of cupola construction, which, when covered with mosaics, produces reflections of light that expand like rays from the central medallion toward the figures surrounding it, was preferred. Such domes are preserved in Kariye Cami, the former church of the Chora, at Istanbul, which was reconstructed and decorated as an act of piety by the logothete, or controller, Theodore Metochites (Metochites, Theodore) in the second decade of the 14th century. Another superb example is found in Fetiye Cami (Church of the Virgin Pammakaristos) in the same city.

      The feeling for colour, which is at its most refined in fragments from the decoration of the Church of the Holy Apostles in Thessaloníki (c. 1315) and at its most intense in the partly well-preserved cycles in the Kariye Cami, informs one of the greatest mosaic works of art, the Deësis panel in the south gallery of Hagia Sophia in Istanbul. In this same panel, the tilting technique reappears (in the cross arms of Christ's halo)—another indication of the retrospection inherent in late Byzantine art.

      No mosaic in the true Palaeologian style has survived outside Byzantium. Reflections of it are found, however, in some of the 13th- and 14th-century works at Venice and in the mosaics executed by Pietro Cavallini (Cavallini, Pietro) in the apse of Sta. Maria in Trastevere in Rome (c. 1290–1300). Some of the characteristics of the style may have been brought to the attention of the Italian artists through portable mosaics, which despite their small size (generally about two by four to eight by ten inches [five by ten to 20 by 25 centimetres]) are imbued with many of the coloristic and technical features typical of monumental mosaics. Byzantine mosaic icons (icon), the production of which was stimulated during the early Palaeologian era, were manufactured for personal devotion more than for the embellishment of churches and were exported in considerable numbers to the West or found their way there as gifts or booty in the politically troubled 14th and 15th centuries. In works whose quality can be compared with the most splendid of the Hellenistic (Hellenistic Age) emblēmata, extremely small tesserae, some measuring less than 0.04 inch (one millimetre) square, were assembled in wax or mastic on a board of fine wood. The tesserae material is often exquisite: silver, gold, and lapis lazuli and other semiprecious stones. The icons depict single figures such as saints, Christ, or the Virgin; single Christian scenes such as the Annunciation (Victoria and Albert Museum, London) and the Crucifixion (Staatliche Museen zu Berlin); or even the full Greek Festival Cycle.

Medieval mosaics in Western Europe

      The prestige, both cultural and political, enjoyed by Byzantium in the Middles Ages (Middle Ages) led to a widespread imitation of its arts. Art objects in great number were imported to the West from Constantinople and other Greek centres. Individuals or communities outside the realm of Byzantium, however, were able to secure Byzantine artisans for the execution of monumental mosaics. Abbot Desiderius of the abbey of Montecassino in Italy, for example, called specialists in many crafts from Constantinople to decorate his new basilica (dedicated AD 1071). Among these were mosaic workers. Of particular importance is the fact that he took care to see that young local artists were trained by the foreigners. This was the pattern that was followed where Byzantine experts were temporarily called in.

      The Norman rulers of Sicily, who vied with the Byzantines for control of the Mediterranean, molded their representational arts largely on those of the great Eastern power. The existence, at Palermo, of a central-plan church (Martorana) embellished according to the classical system has already been noted. In other 12th-century churches in Sicily, the Byzantine element is blended with western Mediterranean traits. Cappella Palatina, the palace chapel of the royal residence at Palermo (c. 1143 and later), for example, is a synthesis of a centralized middle Byzantine church and a basilica. The building therefore called for a hybrid program. According to Western custom, the mosaics of the basilical parts depict narrative cycles: scenes from the Old Testament and from the lives of SS. Peter and Paul. In the centralized part of the church most of the features belonging to the classical system are at hand. There is a bust of the Pantokrator in the dome, surrounded by angels, but as a concession to the longitudinal disposition of the church, the Pantokrator reappears in the apse.

      Martorana and Cappella Palatina were decorated by Byzantine artists, a fact borne out by the brilliant technique, the purity of the Comnenian style, and the adherence to Eastern iconographical prototypes. Two large basilicas are among the highpoints of this Sicilo-Byzantine flowering: the cathedral of Cefalù (c. 1148) and the church of Monreale, the last of the mosaic churches of Sicily (c. 1180–90). Demus has pointed out the extraordinary homogeneity of style and technique in the Monreale mosaics, which constitute the largest decoration of this kind in Italy. He has also shown that the Monreale mosaics are not executed in the refined and softly curved style that dominates in Cappella Palatina and at Cefalù. Monreale is infused with a more agitated and expressive style which, however, has nothing local or provincial about it. It was the late Comnenian style of Constantinople which had then reached Sicily—a testimony to the unbroken artistic contact that existed at this time between the Norman court and Byzantium.

       Venice, for a long time commercially active in the eastern Mediterranean, enjoyed similar but more long-lasting artistic connections with Constantinople. A church that in the 11th century must have looked exotic as well as old-fashioned, St. Mark's (San Marco Basilica) was copied after the venerable Church of the Holy Apostles at Constantinople, an early Byzantine, many-domed type that had long since gone out of favour.

      The mosaic work undertaken at St. Mark's lasted more than two centuries, from the end of the 11th to the middle of the 14th century. The many and marked stylistic disparities can be ascribed in part to the changes that affected Byzantine art during this period; but they may even have been caused by the freer, Western organization of the Venetian workshop, which allowed artists to develop and cultivate their own personal styles. Among the variety of styles, the Byzantine element is dominant, but it is modified by local tendencies and particularly by strong Romanesque impulses.

      The workshops established in Sicily and Venice were active in the neighbouring areas. Mosaics in the cathedral at Salerno (c. 1190) and in the monastery at Grottaferrata near Rome (c. 1200) are regarded as products of the Sicilo-Byzantine school. The apse decoration of the cathedral at Ravenna (early 12th century), of which fragments survive, seems to have been the work of mosaicists from Venice and, in Florence, Venetian artists decorated the dome of the Baptistery (1225–1330). The much later mosaics on the facade of the cathedral at Prague (14th century) are also Venetian.

      In the early Middle Ages, Rome had been able to maintain and defend a mosaic tradition of its own despite the Byzantine hegemony in the arts. At a period when Iconoclasm had loosened the ties between Byzantium and the West, at the end of the 8th century and the beginning of the 9th, the influence of the Roman school extended even into the Carolingian Empire. The apse mosaic of Germigny-des-Prés, France (between 799 and 818), is a product of this influence. In Rome, the pontificate of Paschal I (Paschal I, Saint) (817–824) left three monumental decorations which constitute the best sources concerning the artistic intentions of this time: the sanctuary mosaics of the churches of Sta. Cecilia in Trastevere, Sta. Maria in Domnica, and Sta. Prassede (attached to the latter is the domed chapel of S. Zeno, also fully decorated with mosaics). The iconographic schemes of these 9th-century churches largely reflect local 5th- and 6th-century church decorations. Also remarkable is the return of many of the technical idiosyncrasies of the early Christian period, including the employment of large tesserae for faces and dress and the use of glass for all parts of the composition. The setting of the tesserae is, however, loose and disorganized; and their varying shapes suggest that they are reused cubes taken from older monuments. Stylistically, the mosaics of the Paschal period, with their extreme two-dimensionality, are related to Byzantine mosaics of the 9th century (the cupola of Hagia Sophia, Thessaloníki), but technically the differences could not be greater.

      Little is known of the art in 10th and 11th century Rome. But from the 12th century, a group of works testify to continued inbreeding. The apse decoration of S. Clemente (the 1st half of the 12th century), for example, contains a scroll pattern (rinceaux) reproduced from a 4th-century decoration in a technique that in many respects resembles that of the Paschal mosaics. This isolation, or resistance to foreign influence, seems to have been broken in the 13th century. In 1218, Pope Honorius III asked the doge to send craftsmen for the decoration of S. Paolo Fuori le Mura (1218). Several important mosaics from the later part of the same century reflect the trends current at that time in Byzantine and Italo-Byzantine mosaics. The mosaics by Jacopo Torriti in the apse of the basilica of Sta. Maria Maggiore (c. 1290–1305) are among the finest of these. They show a mingling of Western medieval and Early Christian iconographical features, such as a scene of the crowning of the Virgin surrounded by the scrolls of a fleshy, classicizing rinceaux; but the lower zone with scenes pertaining to Mary reflects Byzantine influence, an influence also seen in the technique and colour scheme of the mosaics.

      Floor mosaics had a renaissance in the West that was unmatched in the Eastern Empire. In the early Middle Ages, the Byzantines developed their particular form of floor covering consisting of a geometrical mosaic made up of pieces of marble of various sizes and shapes (opus sectile) usually with some tessera work added for special coloristic touches. This art, called Cosmati work, spread to the West, in which, however, there was also a revival of the tesselated pavement. This pavement, which had survived the Dark Ages in a very primitive form, reemerged in Italy in the 11th century in greater splendour. There are impressive remains of such floors in many of the larger Italian churches. The fashion spread to other parts of Italy and even to France and Germany. In France, where large floors were produced in quantity in the 12th century, fragments of outstanding quality are found; for example, in Saint-Nicolas' at Reims (last half of 12th century). Cologne seems to have been a leading centre for this art in Germany. The style of the floors is usually one of simple outlines and light colours, though in some cases figures and ornaments appear against dark ground. The programs draw their inspiration from many sources, such as textiles, early floor mosaics, and the sculptural ornamentation of churches. An exceptionally well-preserved example is found in Otranto in the Italian province of Apulia, now Puglia (1163–66), where vast floors depict scenes from the Old Testament and mythology (the ascension of Alexander), representations of the Zodiac, and of the labours of the month. A profusion of monsters and fantastic animals fills out the picture of a decoration cast in the Romanesque iconographic tradition.

Renaissance to modern mosaics

      With the downfall of Byzantium in the 15th century, there perished that milieu in which mosaic had been constantly cultivated and had undergone continuous renewal in response to changing patterns of religious and cultural life. The art lost another foothold in Italy at the beginning of the same century, when changing attitudes about the world and about the function of art eliminated the very bases upon which mosaic had been built. One of the conventions against which the artists of the Renaissance, who were striving for pictorial realism, most strongly rebelled was the use of gold, the other-worldly element most typical of mosaic art.

      Although mosaic continued to be used to a certain extent as church decoration, it was a changed art. Some of its traditional glitter was retained, but essentially mosaics became imitations of painting. These imitative intentions were disastrous and led to the loss of knowledge of how to blend colours and handle materials. In earlier mosaics, there undoubtedly had been a distinction between the leading artist of the project, who drew the composition and oversaw the execution, and the ordinary setters of the tesserae. The leading artist, however, almost certainly took a hand in the setting of special parts and was thoroughly trained in the technical side of the production. Now the preparatory work was divorced from the execution: the artist submitted his cartoon and left its transposition into mosaic to artisans. This drew the lifeblood from the art and caused its degradation.

      In Italy, many of the great painters of the 15th and 16th centuries delivered designs for decorations in mosaic. Best known among these decorations are the works of the Venetian Luigi da Pace after Raphael's cartoon, in the dome of the Chigi Chapel in Sta. Maria del Popolo in Rome (1516), and the mosaics made after the cartoons of Titian, Tintoretto, Giuseppe Salviati, and Paolo Veronese to complete the decoration of St. Mark's in Venice. Among the greatest single undertakings of this kind was the decoration of the dome of St. Peter's in Rome, executed in the last quarter of the 16th century from the cartoons of Cavalier d'Arpino (Cavaliere D'Arpino). St. Peter's also displays some of the most technically striking mosaic reproductions of paintings ever executed—the much admired altar pictures after originals by 16th- and 17th-century masters. Created for the completion and care of the large mosaics of the two great churches, the workshops attached to St. Peter's and to St. Mark's gradually became centres for the manufacture of mosaics. From them, artists were summoned for decorative work in all parts of Europe. The school of mosaics in the Vatican and the workshops in Venice still have a considerable share in the field, together with the school more recently set up for the restoration of the mosaics at Ravenna.

      Nineteenth-century historicism and the breaking down of Neoclassicism's contempt for Byzantine art led to an increasing interest in and demand for mosaics. Improvements in the technique of prefabrication according to the indirect method and in the manufacture of tessera material led to a veritable mass production, which has put its mark on countless churches, town halls and opera houses. Shrill colours and a gleaming, metal-like surface characterize many of these works.

      The modern revival of mosaics had several causes. Scholarship and tourism made the monuments of ancient and medieval mosaics available to an art-loving public. Painting, since the last third of the 19th century engaged in the exploitation of colour, at the turn of the century focussed on the problems of colour as the expression of psychological qualities rather than of the external world. Expressionism, which opened the eyes of artists to the art and artifacts of foreign and distant cultures, also turned their interest towards medieval mosaics. The abstract element which these mosaics contain and which springs from the latent conflict between the design and the tessera pattern made them particularly attractive to artists of the earliest decades of this century such as Marc Chagall and Giovanni Serverini. The texture of mosaic was also an attraction. An American mosaicist, Jeanne Reynal, for example, created abstract compositions in which texture is emphasized by a combination of granulated, pebble-sized, and normal tesserae, sparsely spread over a coloured base of portland cement. Many of these mosaics are small and are hung on the wall like paintings.

      Mosaic's smooth yet faceted surface is ideal for decorating the large, unbroken surfaces of modern architecture. The greatest modern use of mosaic as architectural decoration is in Mexico, a country with a long tradition of folk mural painting. Realizing the potential of the medium for public enjoyment and education, the government in the 1930s and 1940s commissioned many murals with historical and political themes for public buildings. Later, it became desirable to decorate the exterior walls of buildings, and mosaic was the logical alternative to the less durable murals. Often mosaics were designed by mural painters such as Diego Rivera (Rivera, Diego) who, in 1953, designed the immense mosaic on the facade of the Teatro de los Insurgentes. Francisco Eppens also used historical themes in his mosaic decorations of the schools of medicine and dentistry at the National Autonomous University of Mexico (Mexico, National Autonomous University of) (1957), as did Xavier Guerro in the Cine Ermita in Mexico City. Carlos Mérida (Mérida, Carlos), however, created abstract mosaic designs in the Reaseguras Alianza in Mexico City. Among the most prolific Mexican mosaicists was the architect-muralist Juan O'Gorman (O'Gorman, Juan). Of his many mosaic works, the most important is on the exterior walls of the library of the National Autonomous University of Mexico (1951–53), which exemplifies the monumentality of which mosaics are capable. Other works executed by O'Gorman include mosaics on the SCOP, or Secretaría de Communicaciones y Obras Públicas (1952), and a stone mosaic on the facade of the Posada de la Misión Hotel in Taxco. In 1950, O'Gorman began to decorate his own house in Mexico City with phantasmagoric images and symbols from Aztec mythology.

      Mosaic in the strict sense of the word is an art in transition. The conventional tessera mosaic is still largely in use, mainly because of the efficient production methods of modern mosaic firms; yet the distinction between this kind of mosaic and other, mosaic-like techniques is slowly being dissolved. A mixture of cubes and larger pieces of glass, ceramics, or stone is one of the variants that occurs, cubes and objets trouvés (“found objects”) another. After World War II, experiments seem to have moved in the direction of an employment of larger, less regularly cut units. Today, mosaic is just one out of a very wide range of techniques that have as common principle the piecing together of a surface covering with the use of different durable or nondurable materials.

Per Jonas Nordhagen

Pre-Columbian mosaics

      The art of mosaic in pre-Columbian Central America (Native American art) was marked by a combination of great technical skill and widespread use. The representation of a mosaic mask on a stela at Seibal (an upright, freestanding stone slab functioning as a commemorative monument), Guatemala (AD 590), established the early use of the technique in Maya territory, but it became best known from the few specimens surviving from the time of the Aztec empire (c. 1376–1519) and from descriptions of others left by the Spanish conquerors. The Mexican (Mesoamerican civilization) lapidaries worked with obsidian, garnet, quartz, beryl, malachite, jadeite, marcasite, gold, mother-of-pearl, and shell, but turquoise above all constituted their favourite material; the excessive richness of the religious ceremonial gave wide range to its employment in ritual paraphernalia of all sorts. The incrustation was laid upon wood, stone, gold, shell, pottery, and possibly leather and native paper and was held in place by a tenacious vegetal pitch or gum or a kind of cement.

      Masks (mask), shields, helmets, knife handles, staffs, collars, medallions, ear plugs, leggings, mirrors, animal figures, and cult statues received a covering, in whole or part, of small and irregularly shaped pieces of highly polished turquoise, cut to fit tightly together so as to form a brilliant green surface, varied at times with cabochons (a gem cut in convex form, highly polished but not faceted) of turquoise or other material. Most striking and best preserved of the surviving two dozen major specimens of this art are a mask in the British Museum, London, and a shield in the Museum of the America Indian, Heye Foundation, New York City. Minute pieces of turquoise, studded with cabochon turquoises, completely cover the cedar mask and are laid in symmetrical lines around the eyes and mouth and on the nose; eyes and teeth are of shell inlay. Over the wood of the shield, one panelled and three circular borders of mosaic frame a scene that may relate to the worship of the planet Venus; it is estimated that nearly 14,000 pieces of turquoise make up the decoration. A Nahuatl story of a hall at the Toltec city of Tula, the walls of which were covered with fine mosaic, may belong to legend, but a monumental use of the technique was achieved in the mosaic-like treatment of the exterior wall casing of certain buildings. Those at Mitla in the state of Oaxaca are outstanding; bands and panels of simple but striking geometric ornamentation were produced by fitting together small stones of different shapes and sizes, tenoned back into the rubble mass of the wall. Each stone was cut for the spot it occupied, and some were more deeply imbedded than others so that the designs stand out in sharp relief. The effective simplicity of design and precision of workmanship at Mitla are not matched on the elaborate Maya facades—at Uxmal and Chichén-Itzá in Yucatán, for example—where, along with geometrical designs, animal forms also occur.

Frederick O. Waage

Additional Reading

General works

A. Blanchet, La Mosaique (1928); E.W. Anthony, A History of Mosaics (1935, reprinted 1968); P. Fischer, Das Mosaik (1969); H.P. L'Orange and P.J. Nordhagen, Mosaikk (1958; Eng trans., 1966), deals with the history of the art from its beginnings to c. AD 900.

Greek and Roman mosaic

Of the literature on Greek and Roman mosaic, the following works are of particular importance: (pebble mosaic): R.S. Young, “Gordion 1956: Preliminary Report,” Am. J. Archaeology, 61:319–331 (1957); D.M. Robinson, Excavations at Olynthus, vol. 5, 8, and 13 (1933, 1938, 1950). (pebble-tessera mosaic): C.M. Robertson, “Greek Mosaics,” J. Hellenic Stud., 85:72–89 (1965); B.R. Brown, Ptolemaic Paintings and Mosaics and the Alexandrian Style (1957); J. Chandnard, Les Mosaïques de la maison des masques (1933). (floor mosaic—Roman): Colloque sur la mosaïque gréco-romaine, Actes (1965); H.E. Blake, articles on Roman mosaics in Mem. Am. Acad. Rome, 8:7–160, 13:69–214, and 17:81–130 (1930, 1936, 1940); K.M. Phillips, “Subject and Technique in Hellenistic-Roman Mosaics: A Ganymede Mosaic from Sicily,” Art Bull., 42:243–262 (1960); R.P. Henks, Catalogue of the Greek, Etruscan and Roman Paintings and Mosaics in the British Museum (1933); D. Levi, Antioch Mosaic Pavements (1947); I. Lavin, “The Hunting Mosaics of Antioch and Their Sources,” Dumbarton Oaks Papers, no. 17 (1963). H. Stern, “Origine et débuts de la mosaïque murale,” Études d'archéologie classique, vol. 2 (1959).

Early Christian mosaic

M. van Berchen and E. Clouzot, Mosaïques chrétiennes du IV^e au X^e siecle (1924); G. Matthiae, Mosaici medioevali delle chiese di Roma (1967); W. F. Oakeshott, The Mosaics of Rome, from the Third to the Fourteenth Centuries (1967); H. Stern, “Les Mosaïques de l'Église de Sainte-Constance à Rome,” Dumbarton Oaks Papers, no. 12 (1958); C. Cecchelli, I mosaici della basilica di S. Maria Maggiore (1956); C. Ricci, Tavole storiche dei mosaici di Ravenna, 4 vol. (1930–37); F. W. Deichmann, Frühchristliche Bauten und Mosaiken von Ravenna (1958); G. Brusin and P.L. Zovatto, Monumenti paleocristiani di Aquileia e di Grado (1957); J.L. Maier, Le Baptistere de Naples et ses mosaïques (1964); B. Brenk, “Die ersten Goldmosaiken der christlichen Kunst,” Palette (Basel), 38:16–25 (1971), a work concerning the earliest use of gold cubes in mosaics.

Early Byzantine mosaic

G. Brett et al., The Great Palace of the Byzantine Emperors (1947); C. Diehl, M. Le Tourmeau, and H. Saladin, Les Monuments chretiens de Salonique (1918); T. Schmit, Die Koimesis-Kirche von Nikaia (1927); P.A. Underwood, “The Evidence of Restorations in the Sanctuary Mosaics of the Church of the Dormition at Nicaea,” Dumbarton Oaks Papers, no. 13 (1959); M. Aviyonah and M. Schapiro, Israel: Ancient Mosaics (UNESCO 1954–60); E. Kitzinger, Israeli Mosaics of the Byzantine Period (1965); K. Weitzmann, “The Mosaic in St. Catherine's Monastery on Mount Sinai,” Am. Phil. Soc. Proc., 110:392–405 (1966); K.A.C. Creswell, Early Muslim Architecture, 2nd. ed., vol. 1 (1969), including K. Van Berchek, “The Mosaics of the Dome of the Rock in Jerusalem and the Great Mosque in Damascus”; G. Bovini, Mosaici di Ravenna (1956; Eng. trans., Ravenna Mosaics, 1956), and La vita di Cristo nei mosaici di S. Appollinare Nuevo di Ravenna (1959), B.J. Nordhagen, “The Mosaics of John VII (705–707 AD),” Acta, Institutum Romanum Nowegiae, 2: 121–166 (1965); Gunilla Å. Kerström-Hougen, The Calendar and Hunting Mosaics of the Villa of the Falconer in Argos (1974).

Middle and late Byzantine

O. Demus, Byzantine Mosaic Decoration (1948), A. Graber, La Peinture Byzantine (1953; Eng. trans., Byzantine Painting, 1953); T. Whittemore, The Mosaics of Haghia Sophia at Istanbul, 4 vol. (1933–52); P.A. Underwood and E.J.W. Hawkins, “The Mosaics of Hagia Sophia at Istanbul: The Portrait of the Emperor Alexander,” Dumbarton Oaks Papers, no. 15 (1961); E.J.W. Hawkins, “Further Observations on the Marthex Mosaic in St. Sophia at Istanbul,” ibid. 22 (1968); C.A. Mango, “Materials for the Study of the Mosaics of St. Sophia at Istanbul,” ibid. 8 (1962); P.A. Underwood, The Kariye Djami, 3 vol. (1967); E. Diez and O. Demus, Byzantine Mosaics in Greece, Hosios Lucas, and Daphni (1931); A. Grabar and M. Chaizidakis, Greece: Byzantine Mosaics (UNESCO 1960); V.N. Lazarev, Old Russian Murals and Mosaics: From the 11th to 16th Century (1966).

Medieval mosaics in the West

W.F. Oakeshott, The Mosaics of Rome, from the Third to the Fourteenth Centuries (1967); O. Demus, The Mosaics of Norman Sicily (1950); E. Kitzenger, “The Mosaics of the Cappella Palatina in Palermo,” Art Bull., 31:269–292 (1949); The Mosaics of Monreale (1960); A. de Witt (ed.), I mosaici del Battistera di Firenze, 4 vol. (1954–59); H. Kier, Der mittelalterliche Schmuckfussboden (1970); A Prandi, “Pietro Cavallini a S. Maria in Trastevere,” Rivista dell'Istituto Nazionale d'Archeologia e Storia dell'Arte, 1:282–297 (1952); R. Dertel, “Wandmalerei und Zeichnung in Italien,” Mitteilungen des Kunsthistorischen Institutes in Florenz, 5:217–324 (1937–40), on the technique; F. Forlati, “La tecnica dei primi mosaici marciani,” Arte veneta, 3:85–87 (1949); Hetty Joyce, The Decoration of Walls, Ceilings, and Floors in Italy in the Second and Third Centuries A.D. (1981).

Renaissance to modern

The best surveys are those contained in E.V. Anthony, A History of Mosaics (1935, reprinted 1968); and P. Fischer, Das Mosaik (1969). Specific instances are discussed in Frank R. DiFederico, The Mosaics of Saint Peter's: Decorating the New Basilica (1983); and Alvar González-Palacios, The Art of Mosaics: Selections from the Gilbert Collection (1982).

▪ plant disease

      in botany, plant disease caused by various strains of several hundred viruses. Symptoms are variable but commonly include irregular leaf mottling (light and dark green or yellow patches or streaks). Leaves are commonly stunted, curled, or puckered; veins may be lighter than normal or banded with dark green or yellow. Plants are often dwarfed, with fruit and flowers fewer than usual, deformed, and stunted. Flowers may be blotched or streaked (flower breaking), a condition appreciated in certain tulips, often termed Rembrandt tulips, for their attractive and colourful streaking. Mosaic symptoms may be masked or latent, especially at temperatures above 27° C (81° F), and are sometimes confused with nutrient deficiency or herbicide injury. The causal viruses are spread by aphids and other insects, mites, fungi, nematodes, and contact; pollen and seeds can carry the infection as well.

      Mosaic can be avoided by using virus-free seeds and plants, growing resistant varieties, separating new from old plantings, rotating annuals, and observing stringent sanitation and pest-control measures.

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