Two other processes deserve mention, hav ing been used with some success in Germany and England respectively: water-glass and spirit fresco. The first requires special prep aration of the wall-plastering, which is then primed with a thin coat of lime mixed with a special preparation made in Germany, and when dry is successively treated with ferro silicic acid and two coats of water-glass (potas sium silicate). The colors, specially made for this process, are laid on with water, and the finished painting when dry is sprayed with a fixative. It is said to be ill adapted to very damp climates, but has been successfully used, even for out-door wall-paintings, in Paris as well as in Germany. The °spirit fresco" proc ess invented by Gambier Parry and employed by him in the House of Parliament, makes use of wax and certain gums, melted and dissolved in turpentine, as a medium both for sizing the plaster and for carrying the pigment. The wall, thus sized, is primed with white lead and gilder's whitening, and when dry can be painted upon with colors mixed with the medium, as if with oils. The painting can thus be cor rected and touched up without danger, and the result appears to be satisfactory as to perma nence.
Exterior Mural The Egyptians, Greeks and Pompeiians, all executed painted decorations on walls exposed to the weather. In dry climates like those of Egypt, Greece and southern Italy, tempera painting upon carefully prepared stucco is fairly durable. Modern efforts to produce such durable out-of doors paintings on plastered walls have rarely been successful. Hittorff's decorative paintings on the façade of Saint Vincent de Paule in Paris (1846), quickly faded and peeled, although sheltered by a portico. Kaulbach's great ex terior °frescoes') on the New Pinacothek at Munich have fared better; they were presum ably executed in water-glass. The danger to such paintings lies not merely in alternations of dry and damp, heat and frost, but also in the acid fumes from factories, coal-smoke and gas works in modern cities, so that ceramic tiles and mosaic are now generally preferred as the means for color and pictorial effects on the exteriors of buildings. The Germans, it is true, frequently paint ornamental designs on their stuccoed facades, but these decorations have to be- periodically renewed. No really successful process has ever been devised for painting directly on stone or marble, exposed to the weather. The ancients always covered even marble surfaces with a thin coating of very fine lime stucco, sometimes called tic?' before applying their polychromatic deco rations.
Historical Summary.— The articles INTE RIOR DECORATION and PAINTING summarize briefly from different points of view the general history of which that of mural painting is a part. From these the reader may gather some idea of its progress from the prehistoric cave paintings through the Egyptian and Greek civilizations, the brilliant and fantastic Porn peiian and Roman developments, and the sol emn religious representations of the early Christian and Byzantine churches, to its partial eclipse, outside of Italy, in the Gothic period. It was largely displaced in Byzantine art by the more brilliant art of mosaic, and in the Gothic period by that of stained glass, although the painting of conventional patterns on walls, columns and vaults never entirely ceased. It
was in Italy, pre-eminently the land of color decoration, that mural painting was revived in the 13th century by Cimabue, and carried to a marvelous perfection in the 14th century by Giotto and his followers, in the church of Saint Francis at Assisi, the Arena Chapel at Padua and the churches of Santa Croce and Santa Maria Novella at Florence. Another school was early developed in Sienna, and the Tuscan artists were widely employed even in distant cities. In these works, which were anticipatory of the Renaissance, an effort after realism took the place of the Byzantine character of conventional formality of the earlier artists. With the 15th century other ((schools* (i.e., styles of painting led by one or more great artists and their followers) developed in north ren Italy, in Umbria, Rome and later in Venice. The human body was studied; artists painted from models; an increasing mastery of light and-shade and of perspective made possible a corresponding increase in realism. The ear lier pictures symbolized or suggested facts and events; the later ones show the artists' effort to picture a scene as he imagined it would have appeared to an actual spectator. This completely changed the character of all mural painting; the flat wall or ceiling or curved vault was more and more ignored, and the distinction between mural decoration, in its strictest sense, and easel pictures painted merely to fit a given space, was less and less insisted on. Distance, perspective, relief and living action were more and more perfectly repre sented. But the decorative sense was never lost and the grandeur of the composition, its harmony of line and of color, and the absolute beauty of the result, are in many cases so admirable that one cares not at all to think about she wall or the vault. The highest de velopment of this art in fresco was reached in Rome in the first half of the 16th century, espe cially in the Vatican. For majesty and solemn significance the paintings in the Sistine Chapel are unapproached; for richness and splendor those of Raphael in the Stanze, especially' the Camera della Segnatura„ are unsurpassed. For decorations of a lighter sort, Raphael in the Vatican Loggie, and with his pupils in the Farnesina Palace and the Villa Madama and Giulio Romano at Mantua, revived the old Ro man practice of combining mural painting with delicate stucco-relief. In Venice the art of painting in oils received its most brilliant de velopment as applied to the decoration of walls and ceilings at the hands of Titian, Paolo Veronese and Tintoretto in the Ducal Palace. Churches throughout Italy were made splendid with frescoed vaults and painted ceilings. The art declined after 1600, but many brilliant works in both mediums were still executed, and Tie polo (1693-1770) in Venice, Wilrzburg and Madrid, temporarily revived the art with paint ings of a marvelous bravura of conception and execution.