42. Verde-giallo (27).

"These tints," Professor Nobili observes, "are disposed according to the order of the thin mantlings which occasion them; the colour of the thinnest film is numbered 1; then follow in order those produced by a gradual thickening of the medium. I cannot deceive myself in this arrangement, for the thin films which produce the colours are all applied with the same electro-chemical process. The battery, the solution, the distances, &c., are always the same; the only difference is the time the effect is suffered to last. This is a mere instant for the colour of No. 1, a little longer for No. 2, and so on, increasing for the succeeding numbers. Other criterions, however, are not wanting to ascertain the place to which each tint belongs." The scale differs from that of Newton, inasmuch as there is no blue in Nobili's first series and no green in the second: green only appears in the third and fourth series. "The first series," says the Professor, "is remarkable for the fire and metallic appearance of its tints, the second for clearness and brilliancy, the third and fourth for force and richness." The fourth, he observes, has the qualities of the third in a somewhat lesser degree, but the two greens are very nearly alike. It is to be observed, that red and green are the principal ingredients in the third and fourth series, blue and yellow in the second and first. [1] See "Memorie ed Osservazioni, edite et inedite del Cav. Professor Nobili," Firenze, 1834. [2] The colours in some of the compound terms are in a manner mutually neutralising; such terms might, no doubt, be amended. [3] The three first numbers in Newton's scale are black, blue, and white. NOTE S.--Par. 485. A chapter on entoptic colours, contained in the supplement to Goethe's works, was translated with the intention of inserting it among the notes, but on the whole it was thought most advisable to omit it. Like many other parts of the "Doctrine of Colours" it might have served as a specimen of what may be achieved by accurate observation unassisted by a mathematical foundation. The whole theory of the polarization of light has, however, been so fully investigated since Goethe's time, that the chapter in question would probably have been found to contain very little to interest scientific readers, for whom it seems chiefly to have been intended. One observation occurs in it which indeed has more reference to the arts; in order to make this intelligible, the leading experiment must be first described, and for this purpose the following extracts may serve. 3.[1] "The experiment, in its simplest form, is to be made as follows:--let a tolerably thick piece of plate-glass be cut into several squares of an inch and a half; let these be heated to a red heat and then suddenly cooled. The squares of glass which do not split in this operation are now fit to produce the entoptic colours. 4. "In our mode of exhibiting the phenomenon, the observer is, above all, to betake himself, with his apparatus to the open air. All dark rooms, all small apertures (foramina exigua),[2] are again to be given up. A pure, cloudless sky is the source whence we are derive a satisfactory insight into the appearances. 5. "The atmosphere being clear, let the observer lay the squares above described on a black surface, so placing them that two sides may be parallel with the plane of vision. When the sun is low, let him hold the squares so as to reflect to the eye that portion of the sky opposite to the sun, and he will then perceive four dark points in the four corners of a light space. If, after this, he turn towards the quarters of the sky at right angles with that where his first observation was made, he will see four bright points on a dark ground: between the two regions the figures appear to fluctuate. 6. "From this simple reflection we now proceed to another, which, but little more complicated, exhibits the appearance much more distinctly. A solid cube of glass, or in its stead a cube composed of several plates, is placed on a black mirror, or held a little inclined above it, at sun-rise or sun-set. The reflection of the sky being now suffered to fall through the cube on the mirror, the appearance above described will appear more distinctly. The reflection of the sky opposite to the sun presents four dark points on a light ground; the two lateral portions of the sky present the contrary appearance, namely, four light points on a dark ground. The space not occupied by the corner points appears in the first case as a white cross, in the other as a black cross, expressions hereafter employed in describing the phenomena. Before sun-rise or after sun-set, in a very subdued light, the white cross appears on the side of the sun also.[3] "We thus conclude that the direct reflection of the sun produces a light figure, which we call a white cross; the oblique reflection gives a dark figure, which we call a black cross. If we make the experiment all round the sky, we shall find that a fluctuation takes place in the intermediate regions." We pass over a variety of observations on the modes of exhibiting this phenomenon, the natural transparent substances which exhibit it best, and the detail of the colours seen within[4] them, and proceed to an instance where the author was enabled to distinguish the "direct" from the "oblique" reflection by means of the entoptic apparatus, in a painter's study. 40. "An excellent artist, unfortunately too soon taken from us, Ferdinand Jagemann, who, with other qualifications, had a fine eye for light and shade, colour and keeping, had built himself a painting-room for large as well as small works. The single high window was to the north, facing the most open sky, and it was thought that all necessary requisites had been sufficiently attended to. "But after our friend had worked for some time, it appeared to him, in painting portraits, that the faces he copied were not equally well lighted at all hours of the day, and yet his sitters always occupied the same place, and the serenity of the atmosphere was unaltered. "The variations of the favourable and unfavourable light had their periods during the day. Early in the morning the light appeared most unpleasantly grey and unsatisfactory; it became better, till at last, about an hour before noon, the objects had acquired a totally different appearance. Everything presented itself to the eye of the artist in its greatest perfection, as he would most wish to transfer it to canvas. In the afternoon this beautiful appearance vanished--the light became worse, even in the brightest day, without any change having taken place in the atmosphere. "As soon as I heard of this circumstance, I at once connected it in my own mind with the phenomena which I had been so long observing, and hastened to prove, by a physical experiment, what a clear-sighted artist had discovered entirely of himself, to his own surprise and astonishment. "I had the second[5] entoptic apparatus brought to the spot, and the effect on this was what might be conjectured from the above statement. At mid-day, when the artist saw his model best lighted, the north, direct reflection gave the white cross; in the morning and evening, on the other hand, when the unfavourable oblique light was so unpleasant to him, the cube showed the black cross; in the intermediate hours the state of transition was apparent." The author proceeds to recall to his memory instances where works of art had struck him by the beauty of their appearance owing to the light coming from the quarter opposite the sun, in "direct reflection," and adds, "Since these decided effects are thus traceable to their cause, the friends of art, in looking at and exhibiting pictures, may enhance the enjoyment to themselves and others by attending to a fortunate reflection." [1] The numbers, as usual, indicate the corresponding paragraphs in the original. [2] In the historical part, Goethe has to speak of so many followers of Newton who begin their statements with "Si per foramen exiguum," that the term is a sort of by-word with him. [3] At mid-day on the 24th of June the author observed the white cross reflected from every part of the horizon. At a certain distance from the sun, corresponding, he supposes, with the extent of halos, the black cross appeared. [4] Whence the term _entoptic_. [5] Before described: the author describes several others more or less complicated, and suggests a portable one. "Such plates, which need only be an inch and a quarter square, placed on each other to form a cube, might be set in a brass case, open above and below. At one end of this case a black mirror with a hinge, acting like a cover, might be fastened. We recommend this simple apparatus, with which the principal and original experiment may be readily made. With this we could, in the longest days, better define the circle round the sun where the black cross appears," &c. NOTE T.--Par. 496. "Since Goethe wrote, all the earths have been decomposed, and have been shown to be metallic bases united with oxygen; but this does not invalidate his statement."--S. F. NOTE U.--Par. 502. The cold nature of black and its affinity to blue are assumed by the author throughout; if the quality is opaque, and consequently greyish, such an affinity is obvious, but in many fine pictures, intense black seems to be considered as the last effect of heat, and in accompanying crimson and orange may be said rather to present a difference of degree than a difference of kind. In looking at the great picture of the globe, we find this last result produced in climates where the sun has greatest power, as we find it the immediate effect of fire. The light parts of black animals are often of a mellow colour; the spots and stripes on skins and shells are generally surrounded by a warm hue, and are brown before they are absolutely black. In combustion, the blackness which announces the complete ignition, is preceded always by the same mellow, orange colour. The representation of this process was probably intended by the Greeks in the black and subdued orange of their vases: indeed, the very colours may have been first produced in the kiln. But without supposing that they were retained merely from this accident, the fact that the combination itself is extremely harmonious, would be sufficient to account for its adoption. Many of the remarks of Aristotle[1] and Theophrastus[2] on the production of black, are derived from the observation of the action of fire, and on one occasion, the former distinctly alludes to the terracotta kiln. That the above opinion as to the nature of black was prevalent in the sixteenth century, may be inferred from Lomazzo, who observes,--"Quanto all' origine e generazione de' colori, la frigidità è la madre della bianchezza: il calore è padre del nero."[3] The positive coldness of black may be said to begin when it approaches grey. When Leonardo da Vinci says that black is most beautiful in shade, he probably means to define its most intense and transparent state, when it is furthest removed from grey. [1] "De Coloribus." [2] "De Igne." [3] "Trattato," &c. p. 191, the rest of the passage, it must be admitted, abounds with absurdities. NOTE V.--Par. 555. The nature of vehicles or liquid mediums to combine with the substance of colours, has been frequently discussed by modern writers on art, and may perhaps be said to have received as much attention as it deserves. Reynolds smiles at the notion of our not having materials equal to those of former times, and indeed, although the methods of individuals will always differ, there seems no reason to suppose that any great technical secret has been lost. In these inquiries, however, which relate merely to the mechanical causes of bright and durable colouring, the skill of the painter in the adequate employment of the higher resources of his art is, as if by common consent, left out of the account, and without departing from this mode of considering the question, we would merely repeat a conviction before expressed, viz. that the preservation of internal brightness, a quality compatible with various methods, has had more to do with the splendour and durability of finely coloured pictures than any vehicle. The observations that follow are therefore merely intended to show how far the older written authorities on this subject agree with the results of modern investigation, without at all assuming that the old methods, if known, need be implicitly followed. On a careful examination of the earlier pictures, it is said that a resinous substance appears to have been mingled with the colours together with the oil; that the fracture of the indurated pigment is shining, and that the surface resists the ordinary solvents.[1] This admixture of resinous solutions or varnishes with the solid is not alluded to, as far as we have seen, by any of the writers on Italian practice, but as the method corresponds with that now prevalent in England, the above hypothesis is not likely to be objected to for the present. Various local circumstances and relations might seem to warrant the supposition that the Venetian painters used resinous substances. An important branch of commerce between the mountains of Friuli and Venice still consists in the turpentine or fir-resin.[2] Similar substances produced from various trees, and known under the common name of balsams,[3] were imported from the East through Venice, for general use, before the American balsams[4] in some degree superseded them; and a Venetian painter, Marco Boschini, in his description of the Archipelago, does not omit to speak of the abundance of mastic produced in the island of Scio.[5] The testimonies, direct or indirect, against the employment of any such substances by the Venetian painters, in the solid part of their work, seem, notwithstanding, very conclusive; we begin with the writer just named. In his principal composition, a poem[6] describing the practice and the productions of the Venetian painters, Boschini speaks of certain colours which they shunned, and adds:--"In like manner (they avoided) shining liquids and varnishes, which I should rather call lackers;[7] for the surface of flesh, if natural and unadorned, assuredly does not shine, nature speaks as to this plainly." After alluding to the possible alteration of this natural appearance by means of cosmetics, he continues: "Foreign artists set such great store by these varnishes, that a shining surface seems to them the only desirable quality in art. What trash it is they prize! fir-resin, mastic, and sandarach, and larch-resin (not to say treacle), stuff fit to polish boots.[8] If those great painters of ours had to represent armour, a gold vase, a mirror, or anything of the kind, they made it shine with (simple) colours."[9] This writer so frequently alludes to the Flemish painters, of whose great reputation he sometimes seems jealous, that the above strong expression of opinion may have been pointed at them. On the other hand it is to be observed that the term _forestieri_, strangers, does not necessarily mean transalpine foreigners, but includes those Italians who were not of the Venetian state.[10] The directions given by Raphael Borghini,[11] and after him by Armenini,[12] respecting the use and preparation of varnishes made from the very materials in question, may thus have been comprehended in the censure, especially as some of these recipes were copied and republished in Venice by Bisagno,[13] in 1642--that is, only six years before Boschini's poem appeared. Ridolfi's Lives of the Venetian Painters[14] (1648) may be mentioned with the two last. His only observation respecting the vehicle is, that Giovanni Bellini, after introducing himself by an artifice into the painting-room of Antonello da Messina, saw that painter dip his brush from time to time in linseed oil. This story, related about two hundred years after the supposed event, is certainly not to be adduced as very striking evidence in any way.[15] Among the next writers, in order of time prior to Bisagno, may be mentioned Canepario[16] (1619). His work, "De Atramentis" contains a variety of recipes for different purposes: one chapter, _De atramentis diversicoloribus_, has a more direct reference to painting. His observations under this head are by no means confined to the preparation of transparent colours, but he says little on the subject of varnishes. After describing a mode of preserving white of egg, he says, "Others are accustomed to mix colours in liquid varnish and linseed, or nut-oil; for a liquid and oily varnish binds the (different layers of) colours better together, and thus forms a very fit glazing material."[17] On the subject of oils he observes, that linseed oil was in great request among painters; who, however, were of opinion that nut-oil-excelled it "in giving brilliancy to pictures, in preserving them better, and in rendering the colours more vivid."[18] Lomazzo (a Milanese) says nothing on the subject of vehicles in his principal work, but in his "Idea del Tempio della Pittura,"[19] he speaks of grinding the colours "in nut-oil, and spike-oil, and other things," the "and" here evidently means _or_, and by "other things" we are perhaps to understand other oils, poppy oil, drying oils, &c. The directions of Raphael Borghini and Vasari[20] cannot certainly be considered conclusive as to the practice of the Venetians, but they are very clear on the subject of varnish. These writers may be considered the earliest Italian authorities who have entered much into practical methods. In the few observations on the subject of vehicles in Leonardo da Vinci's treatise, "there is nothing," as M. Merimée observes, "to show that he was in the habit of mixing varnish with his colours." Cennini says but little on the subject of oil-painting; Leon Battista Alberti is theoretical rather than practical, and the published extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture. Borghini and Vasari agree in recommending nut-oil in preference to linseed-oil; both recommend adding varnish to the colours in painting on walls in oil, "because the work does not then require to be varnished afterwards," but in the ordinary modes of painting on panel or cloth, the varnish is omitted. Borghini expressly says, that oil alone (senza più) is to be employed; he also recommends a very sparing use of it. The treatise of Armenini (1587) was published at Ravenna, and he himself was of Faenza, so that his authority, again, cannot be considered decisive as to the Venetian practice. After all, he recommends the addition of "common varnish" only for the ground or preparation, as a consolidating medium, for the glazing colours, and for those dark pigments which are slow in drying. Many of his directions are copied from the writers last named; the recipes for varnishes, in particular, are to be found in Borghini. Christoforo Sorte[21] (1580) briefly alludes to the subject in question. After speaking of the methods of distemper, he observes that the same colours may be used in oil, except that instead of mixing them with size, they are mixed on the palette with nut-oil, or (if slow in drying) with boiled linseed-oil: he does not mention varnish. The Italian writers next in order are earlier than Vasari, and may therefore be considered original, but they are all very concise. The treatise of Michael Angelo Biondo[22] (1549), remarkable for its historical mistakes, is not without interest in other respects. The list of colours he gives is, in all probability, a catalogue of those in general use in Venice at the period he wrote. With regard to the vehicle, he merely mentions oil and size as the mediums for the two distinct methods of oil-painting and distemper, and does not speak of varnish. The passages in the Dialogue of Doni[23] (1549), which relate to the subject in question, are to the same effect. "In colouring in oil," he observes, "the most brilliant colours (that we see in pictures) are prepared by merely mixing them with the end of a knife on the palette." Speaking of the perishable nature of works in oil-painting as compared with sculpture, he says, that the plaster of Paris (gesso) and mastic, with other ingredients of which the ground is prepared, are liable to decay, &c.; and elsewhere, in comparing painting in general with mosaic, that in the former the colours "must of necessity be mixed with various things, such as oils, gums, white or yolk of egg, and juice of figs, all which tend to impair the beauty of the tints." This catalogue of vehicles is derived from all kinds of painting to enforce the argument, and is by no means to be understood as belonging to one and the same method. An interesting little work,[24] still in the form of a dialogue (Fabio and Lauro), appeared a year earlier; the author, Paolo Pino, was a Venetian painter. In speaking of the practical methods Fabio observes, as usual, that oil-painting is of all modes of imitation the most perfect, but his reasons for this opinion seem to have a reference to the Venetian practice of going over the work repeatedly. Lauro asks whether it is not possible to paint in oil on the dry wall, as Sebastian del Piombo did. Fabio answers, "the work cannot last, for the solidity of the plaster is impenetrable, and the colours, whether in oil or distemper, cannot pass the surface." This might seem to warrant the inference that absorbent grounds were prepared for oil-painting, but there are proofs enough that resins as well as oil were used with the _gesso_ to make the preparation compact. See Doni, Armenini, &c. This writer, again, does not speak of varnish. These appear to be the chief Venetian and Italian authorities[25] of the sixteenth and part of the following century; and although Boschini wrote latest, he appears to have had his information from good sources, and more than once distinctly quotes Palma Giovane. In all these instances it will be seen that there is no allusion to the immixture of varnishes with the solid colours, except in painting on walls in oil, and that the processes of distemper and oil are always considered as separate arts.[26] On the other hand, the prohibition of Boschini cannot be understood to be universal, for it is quite certain that the Venetians varnished their pictures when done.[27] After Titian had finished his whole-length portrait of Pope Paul III. it was placed in the sun to be varnished.[28] Again, in the archives of the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), "per far la vernise da invernisar la Pala dell' altar grando," and the same day a second entry appears of a payment to a painter, "per esser venuto a dar la vernise alla Pala," &c.[29] It is to be observed that in both these cases the pictures were varnished as soon as done;[30] the varnish employed was perhaps the thin compound of naphtha (oglio di sasso) and melted turpentine (oglio d'abezzo), described by Borghini, and after him by Armenini: the last-named writer remarks that he had seen this varnish used by the best painters in Lombardy, and had heard that it was preferred by Correggio. The consequence of this immediate varnishing may have been that the warm resinous liquid, whatever it was, became united with the colours, and thus at a future time the pigment may have acquired a consistency capable of resisting the ordinary solvents. Not only was the surface of the picture required to be warm, but the varnish was applied soon after it was taken from the fire.[31] Many of the treatises above quoted contain directions for making the colours dry:[32] some of these recipes, and many in addition, are to be found in Palomino, who, however defective as an historian,[33] has left very copious practical details, evidently of ancient date. His drying recipes are numerous, and although sugar of lead does not appear, cardenillo (verdigris), which is perhaps as objectionable, is admitted to be the best of all dryers. It may excite some surprise that the Spanish painters should have bestowed so much attention on this subject in a climate like theirs, but the rapidity of their execution must have often required such an assistance.[34] One circumstance alluded to by Palomino, in his very minute practical directions, deserves to be mentioned. After saying what colours should be preserved in their saucers under water, and what colours should be merely covered with oiled paper because the water injures them, he proceeds to communicate "a curious mode of preserving oil-colours," and of transporting them from place to place. The important secret is to tie them in bladders, the mode of doing which he enters into with great minuteness, as if the invention was recent. It is true, Christoforo Sorte, in describing his practice in water-colour drawing, says he was in the habit of preserving a certain vegetable green with gum-water in a bladder; but as the method was obviously new to Palomino, there seems sufficient reason to believe that oil-colours, when once ground, had, up to his time, been kept in saucers and preserved under water.[35] Among the items of expense in the Treviso document before alluded to, we find "a pan and saucers for the painters."[36] This is in accordance with Cennini's directions, and the same system appears to have been followed till after 1700.[37] The Flemish accounts of the early practice of oil-painting are all later than Vasari. Van Mander, in correcting the Italian historian in his dates, still follows his narrative in other respects verbatim. If Vasari's story is to be accepted as true, it might be inferred that the Flemish secret consisted in an oil varnish like copal.[38] Vasari says, that Van Eyck boiled the oils with other ingredients; that the colours, when mixed with this kind of oil, had a very firm consistence; that the surface of the pictures so executed had a lustre, so that they needed no varnish when done; and that the colours were in no danger from water.[39] Certain colours, as is well known, if mixed with oil alone, may be washed off after a considerable time. Leonardo da Vinci remarks, that verdigris may be thus removed. Carmine, Palomino observes, may be washed off after six years. It is on this account the Italian writers recommend the use of varnish with certain colours, and it appears the Venetians, and perhaps the Italians generally, employed it solely in such cases. But it is somewhat extraordinary that Vasari should teach a mode of painting in oil so different in its results (inasmuch as the work thus required varnish at last) from the Flemish method which he so much extols--a method which he says the Italians long endeavoured to find out in vain. If they knew it, it is evident, assuming his account to be correct, that they did not practice it. [1] See "Marcucci Saggio Analitico-chimico sopra i colori," &c. Rome, 1816, and "Taylor's Translation of Merimée on Oil-painting," London,