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 Santa 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. 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 ’40s 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, 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 (1957), as did Xavier Guerro in the Cine Ermita in Mexico City. Carlos Mérida, 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. 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.