It may be doubted whether any works of art produced in later times could have withstood the trials to which the mural paintings of Pompeii have been subjected from the action of heat and damp, the latter for centuries, without serious damage. The expression of Vitruvius that they would last for ever has been so far justified. The processes of the ancients were not limited to fresco-painting; they were familiar with others of great beauty and durability, but these do not enter within the scope of the present notice. The construction of the walls and the system of plastering then in use are more important subjects of inquiry in connexion with fresco. Those unsurpassed builders, the Romans, faced walls intended to be painted, with a lining of bricks set on edge, detached by a small space from the main structure to which it was secured with leaden clamps. This was a precaution against damp well worthy of imitation. Generally, three preparatory coats of plaster were laid on this brick facing or on any other description of wall, the first consisting of lime mixed with pounded brick and pozzolana, the other two with lime and pozzolana. The finishing coat was frequently composed of lime and pounded marble, which was susceptible of an exquisite polish, after which it was painted by durable processes, the secret of which is now lost. For fresco-painting the last coat or intonaco consisted of lime mixed with sand only. A long gap now occurs in the progress of mural painting. Its practice is feebly illustrated in tombs and catacombs, interesting historically, but of little value technically. Finally it was displaced for a time by mosaic, but it was again revived in the 13 th century, that great epoch of the resuscitation of the fine arts. The works of Giunta Pisano and some of his contemporaries in the upper church of St Francis at Assisi, executed in the first half of the 13th century, clearly indicate a knowledge of a system of fresco. In a history of the practice of this art these mural paintings, with those of Cimabue and his colleagues or assistants, and those by Giotto and his followers, deserve special consideration. They illustrate the early processes of fresco and mural painting upon which all the methods subsequently followed were based. It is evident from the structure of the interior of the beautiful upper church of St Francis that the architect did not provide for its being painted internally. It was complete in its admirable masonry, and when it was determined to paint it, the only preparatory process possible was to cover the aslar with a thin coat of intonaco about one-eighth of an inch in thickness. Any plan of preparatory coats of plaster in the Roman manner would have buried the string courses and other mouldings, and ruined the proportions of the piers. True fresco-painting under such conditions was consequently very difficult, for the thin intonaco, laid on a stone wall which could not be soaked with water, of necessity dried rapidly. The mixed art of fresco and distemper which was thus made imperative at Assisi prevailed in mural painting, with certain modifications, for a long period everywhere.!
The following is a brief statement of the methods of Giunta Pisano and Cimabue. Both artists practised, if they did not inaugurate, the system of outlining their subjec⅛ on the walls, which continued for two centuries, till it was abandoned for the better plan of preparing cartoons* A sketch was first made, and w as squared in the usual manner with vertical and horizontal lines drawn to scale. The space to be painted was then squared proportionately, and, guided by the squares, the artist outlined his subject full size with charcoal on the wall. This done, with a hair pencil and some ochre mixed with water he passed over the general lines, and then brushed off the charcoal; he next marked in the entire composition with red “'terra rossa* mixed with water only, this time entering more into detail, and even indicating the chiaroscuro. Where the ancient intonaco has fallen off, these red outlines are visible; they have a mysterious grandeur, and those by the hand of Cimabue prove the possession on his part of freedom and power of drawing. Over these outlines the intonaco was spread in portions, and on it the artist marked the squares once more, and drew the outlines of the figures he meant to paint. . That the intonaco was prepared in sections is proved, not only by the visible lines in the plaster, but also by the falling off of the leg of a figure, showing the cut made by the artist when he had finished his work. The cut follows the outline of the limb, and this process suffices to show that fresco-painting was practised in the first half of the 13th century, if any doubt should be entertained. The intonaco being spread, the artist painted his subject in a slight manner with terra rossa, laying in the chiaroscuro and details, after which the plaster was allowed to dry. The picture thus prepared was then coloured in distemper, and completed in every part. By the aid of Vasari and of Cennino Cennini a pupil of the school of Giotto, who completed his treatise on painting on the 31st July 1437, we have clear statements of the methods of mural painting followed by the Byzantine artists, and subsequently by the Italians. Cennino, in the most express terms, states that mural pictures, although commenced in fresco, were always finished in distemper. The distempers used were a mixture of egg, including both the albumen and the yolk, with the milky fluid which exudes from twigs of the fig tree; size made from glue or from gum tragacanth is also mentioned. A list of the colours employed by Giotto and his pupils and successors is given below; and the same, there can be little doubt, were iu use on the part of Giunta, of Cimabue, and their contemporaries. Amongst these white lead played an important part in painting on panels and on walls. All who are familiar with old pictures must have frequently seen those of black Madonnas and saints, held iu especial veneration for their sanctity and antiquity. The colours with which they were painted were freely mixed with white lead and with the yolk and albumen of egg, which darkens whilst the white lead oxidizes; hence their present state.
This partially explains the singular appearance presented by the mural pictures of Giunta at Assisi, in which the shadows are red executed in fresco, and the lights painted in distemper are black. The explanation is not entirely satisfactory, however, for the change is not universal, and in a considerable number of the pictures the colours have not changed; but wherever damp has penetrated, the paintings have become very dark; the microscope would probably show that this is due to the presence of fungus, the produce of the egg distemper. As the works attributed to Cimabue are for the most part in better preservation than those given to Giunta, they suggest that this great artist, who did so much for design, also improved the technical processes of mural art. He undoubtedly carried frescopainting further, although on thin intonaco; but he prepared for the finishing processes as his predecessors had done. This statement is based upon the examination of a Madonna and Child with Angels in the lower church of St Francis, which is executed in the same manner as the pictures in the upper church ascribed to Giunta. This fragment is so noble in design, the heads are so beautiful, the whole work is so much better than the picture of the Borgo Allegri, now in St Maria Novella Florence, that although in its method it is like the works of Giunta, in design it is far beyond his powers. Cimabue’s method of outlining on the wall has been described; but there are traces of his use of the stylus, to which he had recourse when he wished to alter an outline after the work was begun, and it is therefore evident that the plaster was damp when he had recourse to this instrument. His preparations in fresco being dry, he proceeded to paint the shadows of flesh with terra vert in distemper, and then modelled the features with the requisite colours. That he heightened the lights with white lead is apparent, for these have become black even in places which damp did not reach. A glaring example of this is the table-cloth in a picture of the Marriage at Cana in Gallilee, which, once white, is now an intense black; the plates, viands, and vases upon it are unchanged in colour; these no doubt are in pure fresco, which explains the difference.
We can form no idea now of the splendid appearance which the paintings in the interior of St Francis presented when newly done. There are abundant traces of the use of a mordant for gilding, showing that the high lights upon dresses and the edges of folds were gilt, as well as embroideries on the borders, and on the aureoles of saints. It is obvious that such ideas were derived from mosaics, in which the lights sparkle with gold. Regarded simply as decorative art, these paintings at Assisi, with their clear bright colouring, the rich gilding, and with the windows filled with coloured glass, must have been magnificent. The art was very conventional, still the beginnings are perceptible of a higher imitative system, and of a growing appreciation of truth to nature. The heads of angels are characterized by expressive beauty; the bride in the Marriage at Cana has a very pleasing face, and even the idea of portraiture is observable; the look of surprise in the countenance of the husband is naturally expressed, and with good taste. Those who have not seen these paintings, and only judge of the merits of Cimabue by his altarpieces at Florence, can have little conception of the ability of this remarkable artist.
Beneath the paintings of Cimabue, and under the gallery which represents a triforium, range the mural pictures of Giotto and his contemporaries or pupils. By Giotto the art of fresco received a new impetus; he continued the mixed method then prevalent, but with a more moderate use of distemper, and laid the foundation of the system carried to perfection by his greatest successors. The part of the wall which was assigned to him apparently admitted of thicker plastering, for he caused preparatory coats of plaster to be spread with due care; on the last of these, when dry, he no doubt made his outlines according to the manner of his predecessors, and over these the intonaco was distributed with singular dexterity. Plastering in his time was a branch of fine art, so that it is at all times difficult to discover the joinings in the works of Giotto and his followers. An account of his method of mural painting will convey a clear idea of the technical processes improved by him and followed by other artists after him.
The lime prepared for the intonaco having been kept till it had parted with much of its caustic quality, was mixed with sand in the proportion of two of sand to one of lime. The pigments used were :—White—biancosangiovanni, or lime carefully ground with pure water and dried in the sun in the form of cakes; black—charcoal of vinewood, a black chalk, or lamp black; red—cinabrese, a red earth of intense colour, and sinopia, a lighter red, also an earth, and burnt ochre; amatista—not now known by this name, but a fine purple red; green—terra vert; yellow—two qualities of ochre, dark and light, and giallolino, which resembled Naples yellow in tone. This is a very moderate palette, but it was supplemented by the colours subsequently applied in distemper. These were orpiment, cin-abro (a red oxide), German blue (apparently a cobalt), vermilion, lake, verdigris, indigo, and white lead. When the picture was commenced in fresco, particular grounds were laid on the wet plaster in preparation for the colours which were to follow; for instance, the sky to be painted blue in distemper was prepared with a deep red (cinabrese) in fresco. The virgin’s blue robe was first grounded with black mixed with red, and then painted with blue mixed with size prepared from glue, for red of egg would have made it green. The blue, however, has frequently become a bright green, spite of this care. There are numerous examples of these methods in pictures, extending from the age of Giotto to that of Raphael. In a painting by Lippo Memmi at Assisi a dark rich red in distemper is laid over a preparation of light red in fresco. By Ghirlandajo a brown robe has been coloured in tempera over pale grey in fresco. The dark purple robe of the Cardinal Bonaventura in the fresco called the Dispute on the Sacrament, by Raphael, is spread over a preparation of red. Many other cases might be cited were it necessary. The most singular of all was the preparation for painting trees and bushes by a ground in fresco of black, on which the leaves, branches, sprays, buds, and flowers were executed of the proper colours in distemper. Illustrations of this custom are observable in pictures by Orcagna, Pietro Laurati, Simone Μemmi, Masolino, Paolo Ucello, and many other artists; it did not survive the 15th century, and it is due to Masaccio to point out that he appears to have been the first to escape from this commonplace conventionality.
The methods of mixing colours and tints and their use in painting were reduced to system, whether for painting drapery or the nude. It was usual to prepare three pots of each colour carefully graduated. Thus, for instance, in the preparation of a flesh tint, a certain quantity of lime, biancosangiovanni, was mixed with red; in another pot the same red, with much more lime; two equal portions of these tints were mixed in the third pot: thus three equal gradations were secured. A head, hand, or any part of the body being drawn on the wet plaster with fine lines with the brush, the shadows were painted with terra vert, then, the lightest flesh tint being taken, the lights were put in. This done, the middle tint was applied, the junctions between the two tints being carefully softened; next the darker colour was laid in, all these tones being fused together in a proper way. The operations were repeated till sufficient solidity —impasto—was obtained. Another and much lighter tone served to mark the high lights, such as those on the nose, chin, and parts of the ears; lastly, the small and most brilliant points of light were touched with pure white, and the whites of the eyes were painted. The artist next outlined the nostrils, eyelids, and apertures of the ears with black, touched in the lower eyelids and the eyebrows with shades of sinopia, and with the same colour the nostrils, upper lip, and the line between the lips. The hair was broadly shaded with terra vert, and washed over with light ochre; then the locks were defined with dark ochre, and the lights pencilled with a much lighter tint of the same; lastly, the outlines were strengthened with sinopia. Such usually were the methods pursued by Giotto and his followers. It is evident that painting thus, according to a fixed system, a master and his trained pupils could act together and harmonize their work in a manner otherwise unattainable. At the same time the individuality of the artist was not obliterated by this prevalence of rule. In the frescos attributed to Giotto and his followers or compeers, it is not difficult to distinguish the different handiwork. In some the green shadows are modified with a warmer tint; in others the results are cold and formal; some paint with soft gradations, others in a harder manner, but the difference between the artists is still more observable in the drawing and proportions of the figures. As guiding cartoons were not prepared by the master; probably the assistants or pupils were only provided with his sketches, which they enlarged on the wall with such skill as they possessed; hence the varieties of proportion which are so remarkable.
Draperies were painted with graduated colours prepared in the same way; the lights, according to the usage of the Tuscan school, were heightened with pure white, and the shadows were glazed with washes of unmixed colour, showing that the intonaco must have been damp when these were applied or they would not have adhered. Thus in these pictures the most important part of the work was pure fresco, whilst the tempera, although undoubtedly used, was less freely applied by Giotto than by his master Cimabue and his predecessors, judging from the mural paintings at Assisi To the taste and genius of Giotti was owing this great improvement in the technical processes of mural painting.
The architectural details, where they occur as accessories or backgrounds, are carefully drawn and painted with infinite grace, and as architectural designs they are singularly beautiful, especially...
