compared to that of Rubens; it is juicy, transparent, and clear;
his execution is light and graceful." No sounder model
could be taken for modern work. The high-water mark of
achievement in fresco painting was however reached by a greater
than Luini — by Michelangelo in his painting of the Sistine Chapel
roof. Considering that since his boyhood he had had no practical
experience of the fresco process, and refused the commission as
long as he could because he was not a painter but a sculptor,
Buonarroti's technical success in the manipulation of the difficult
process is still more astounding than the aesthetic result of the
work as a creation of imaginative genius. He had to paint for
the most part lying on his back in a sort of cradle, and working
with his arms above his head, and had no skilled assistants;
yet there is no quality in the work that strikes us more than its
freshness and air of easy mastery, as if the artist were playing
with his task. The fusion of the lights and shadows through
the most delicate half-tones is accomphshed in that melting
fashion for which the Italians used the term sfumato or
" misty, " while at the same time the touches are crisp and firm,
the accent here and there decided; and the artist's incomparable
mastery of form gives a massive solidity to the whole (see fig.
34, Plate X.)
In our own times and in English-speaking circles the fresco process has been discredited owing to the comparative failure of the experiments connected with the Houses of Parliament. On the condition of the frescoes there, as well as on that of the pictures in various other media, a series of Memoranda were made by Professor Church, and a select committee of the House of Lords took evidence on the subject as late as December 1906. Most of the frescoes executed in the forties and fifties of the igth century had got into a deplorable state; but Church's belief was that the main cause of the decay was the sulphurous acid with which, owing to the consumption of coal and gas, the air of London is so highly charged. The action of this acid — a million tons of which are said to be belched out into the London atmosphere in every year — turns the carbonate of lime which forms the surface of the fresco into a sulphate, and it ceases to retain its binding power over the pigments. " The chemical change, " he reports, " is accompanied by a mechanical expansion which causes a disruption of the ground and is the main cause of the destruction of the painting." It is a remarkable fact, however, that one of the frescoes in question. Sir John Tenniel's " St Cecilia, " completed in 1S50, painted very thinly and on a smooth surface, lasted well, and opposed " a considerable measure of successful resistance for nearly half a century on the part of a pure fresco to the hostile influence of the London atmosphere " (Church, Memorandum, iv. 1896).
Abroad, experience was more favourable. The earliest frescoes of the modern revival — those by Cornelius and his associates from the Casa Bartholdy at Rome — are in a fairly good state in the National Gallery at Berlin. Such too is the condition of Cornelius's large fresco in the Ludwigskirche at Munich. The best modern frescoes, from the artistic point of view, in all Europe are those of about 1850 by Alfred Rethel in the town-hall at Aix-la-Chapelle, and they are well preserved. The exterior frescoes on the Pinacotek at Munich have on the other hand mostly perished; but the climate of that city is severe in winter, and nothing else was really to be expected. We must not expect carbonate of lime to resist atmospheric influences which affect to a greater or less degree all mineral substances.
§ 36. Frcsco-Secco. — (See Charles Heath Wilson, in appendix to Second Report of the Commissioners on the Fine Arts, London, 1843, p. 40; Church, Chemistry of Paints and Painting, 1901, p. 278).
The process called " fresco-secco " is a method of lime painting on a plaster surface that has been allowed to dry. It is described by Theophilus in the Schedida of about a.d. 1 100; and Mr Charles Heath Wilson in 1843 wrote of it as " extensively used in Italy at present and with great success." It is of course obvious that paintings must often be executed on walls the plastering of which is already dry, and on which the true fresco process is impracticable. Some kind of painting in tempera is thus needful, and " fresco-secco " uses for this the lime that is the very constituent of the plaster. The process is thoroughly to drench the dry surface of the plaster the night before with water with which a little lime or baryta water has been mixed, and to renew the wetting the next morning. The artist then fixes up his cartoon, pounces the outlines, and sets to work to paint with the same pigments as used in buon fresco mixed with lime or baryta water or with a little slaked lime. If the wall become too dry a syringe is used to wet it. The directions given by Theophilus (i. 15) correspond with this modern practice. " When figures or representations of other things, " he says, " are to be delineated on a dry wall, it must be forthwith moistened with water tiU it is thoroughly wet. On this wet ground all the colours must be laid that are required, and they must be all mixed with hme, and will dry with the wall so that they adhere to it." Mr C. H. Wilson praises the work for its convenience, economy, and ease of execution, and notes that " for ornament it is a better method than real fresco, as in the latter art it is quite impossible to make the joinings at outlines owing to the complicated forms of ornaments, " but says that " it is in every important respect an inferior art to real fresco. Paintings executed in this mode are ever heavy and opaque, whereas fresco is light and transparent." He declares also for its durability, but Professor Church states what seems obvious, that " the fixation of the pigments ... is less complete " than in real fresco though depending on the same chemical conditions(Second Report, 1843, p. ^o; Chemistry, p. 279).
§ 37. Stcreochromy or Water-Glass Painting. — (See Chemischtechnische Bibliothek, Band Ixxviii., Die Mineral-Malerei, von A. Keim, Wien, &c., 1881; Rev. J. A. Rivington in Journal of the Society of Arts, No. 1630, Feb. 15, 1884; Mrs Lea Merritt and Professor Roberts Austin in Journal of the Society of Arts, No. 2246, Dec. 6, 1895; F. G. Cremer, Beitrdge zur Technik der M monumental-M alverfahren, Düsseldorf, 1S95).
Akin to " fresco-secco, " in that a mineral agent is used to secure the adhesion of the colouring matter to the plaster, is the process known as stcreochromy or water-glass painting. It is not a traditional process, but an outcome of comparatively modern chemical research, and is not yet a century old. It is based on the properties of the substance called water-glass, a silicate of potassium or of soda, perfected by the German chemist Von Fuchs about 1825. A process of painting called " stcreochromy " was soon after evolved, in which pigments of the same kind as those used in fresco, mixed only with distilled water and laid on a prepared plaster ground, were afterwards fi-xed and securely locked up by being drenched with this substance, which is equivalent to a soluble glass. Some of the mural paintings in the Houses of Parliament, notably those by Maclise, were executed in this process. Improvements were more recently effected in the process with which the names of Keim and Recknagel of Munich are connected, and in this form it has been used a good deal in Germany in the last quarter of the 19th century both in interiors and in the open air. For example, in 1881 Professor Schraudolph of Munich painted in this process the front of the Hotel Bellevue in that city. This improved water glass painting was introduced to notice in England in a paper read before the Society of Arts by the Rev. J. A. Rivington on the 13th of February 1S84, and printed in the Journal of the society, No. 1630. A more recent description is contained in F. G. Cremer's Beitrdge.
The recipe for the preparation of the actual medium is as follows: 15 parts pounded quartz sand, 10 parts refined potash, i part powdered charcoal are mixed together and fused for 6 to 8 hours in a glass furnace. The resultant mass when cold is reduced to powder and boiled for 3 or 4 hours in an iron vessel with distilled water till it dissolves and yields a heav^' syrupy liquor of strongly alkaline reaction. This can be diluted with water, and in the process is applied hot.
The ground is very carefully prepared, and over a thoroughly sound and dry backing a thin coat of plaster is laid, composed of only I part lime to 5 or 8 parts selected sand and pounded marble with a slight admixture of infusorial earth. The object is to obtain a homogeneous porous ground that can be thoroughly permeated with the solution, and to help to secure this the intonaco when dry
