[195]. This truth, about the mutual influence of colours in juxtaposition, was well put by Sir Charles Eastlake when he wrote, in his Materials for a History of Oil Painting, ‘flesh is never more glowing than when opposed to blue, never more pearly than when compared with red, never ruddier than in the neighbourhood of green, never fairer than when contrasted with black, nor richer or deeper than when opposed to white.’
[196]. Vitruvius describes the fresco process in his seventh Book. See Note on ‘Fresco Painting’ at the end of the ‘Introduction’ to Painting, postea, p. 287. This chapter is one of the most interesting in the three ‘Introductions.’
[197]. Travertine, next to marble, makes when burnt the whitest lime (see § 30, ante, p. [86]). From this lime the fresco white, called bianco Sangiovanni, is made, and Cennini gives the recipe for its preparation in his 58th chapter. The ordinary lead white (biacca) cannot be used in fresco.
[198]. The word ‘tempera’ is used by Vasari and other writers as a noun meaning (1) a substance mixed with another, as a medium with pigments (2) a liquid in which hot steel is plunged to give it a particular molecular quality (ante, p. [30]) (3) the quality thus given to the steel (ante, p. [32]), while (4) it has come to mean in modern times, as in the heading of this Note, a particular kind of painting. It is really to be regarded as the imperative of the verb ‘temperare,’ which alike in Latin and in Italian means ‘to divide or proportion duly,’ ‘to qualify by mixing,’ and generally ‘to regulate’ or ‘to discipline.’ ‘Tempera’ thus means strictly ‘mix’ or ‘regulate.’ It is used in the latter sense in metallurgy, as the liquid which Vasari calls (ante, p. [30]) a ‘tempera’ (translated ‘tempering-bath’) regulates the amount of hardness or elasticity required in the metal, and the quality the steel thus receives is called (ante, p. [32]) its ‘temper.’ In the case of painting the ‘tempera’ is the binding material mixed with the pigment to secure its adhesion to the ground when it is dry. The painting process is, in Italian, painting ‘a tempera’ ‘with a mixture,’ and our expression ‘tempera painting’ is a loose one. For the form of the word we may compare ‘recipe,’ also employed as a substantive but really an imperative meaning ‘take.’
Strictly speaking any medium mixed with pigments makes the process one ‘a tempera.’ Many substances may be thus used, some soluble in water, as size, gum, honey, and the like; others insoluble in water, such as drying oils, varnishes, resins, etc., while the inside of an egg which is in great part oleaginous may have a place between. It is not the usage however to apply the term ‘tempera’ to drying oils or varnishes, and a distinction is always made between ‘tempera painting’ and ‘oil painting.’ See Note on ‘Tempera Painting,’ postea, p. 291.
[199]. This practice of covering wooden panels with linen and laying over this the gesso painting ground was in use in ancient Egypt. In fact the methods described by Cennini of preparing and grounding panels are almost exactly the same as those used in ancient Egypt for painting wooden mummy-cases. Even the practice, so much used in early Italian art, of modelling details and ornaments in relief in gesso and gilding them, is common on the mummy-cases. On the subject of gesso see Note 5 on p. 249.
[200]. Vasari’s expression ‘rosso dell’ uovo o tempera, la quale è questa’ calls attention to the fact, to which his language generally bears testimony, that he looked upon the yolk of egg medium as the tempera par excellence. When he uses the term ‘tempera’ alone he has the egg medium in his mind, and the size medium is something apart. See this chapter throughout.
[201]. Tempera painting has had a far longer history and more extensive use than any other kind. The technique predominated for all kinds of painting among the older Oriental peoples and in classical lands, and was in use both on walls and on panels in Western Europe north of the Alps during the whole mediaeval period, while south of the Alps and at Byzantium it was to a great extent superseded for mural painting by fresco, but remained in fashion for panels till the end of the fifteenth century. After the fifteenth century the oil medium, as Vasari remarks, superseded it entirely for portable pictures, and partly for work on walls and ceilings, but in our own time there has been a partial revival of the old technique. See Note on ‘Tempera Painting,’ postea, p. 291.
The whole question of the different vehicles and methods used in painting at various periods is a difficult and complicated one, and too often chemical analysis fails to give satisfactory results owing to the small amount of material available for experiment. Berger, in his Beiträge zur Entwicklungs-Geschichte der Maltechnik, an unfinished work that has already run to a thousand pages, goes elaborately into the subject, but has to admit that many points are still doubtful. It makes comparatively little difference what particular medium is used in tempera painting, but it is of great importance to decide whether a particular class of work is in tempera or in fresco. In connection with this Berger has reopened the old controversy as to the technique of Pompeian wall paintings, which have been accepted as frescoes, on the authority of Otto Dönner, for a generation past. There are difficulties about Pompeian work and it is well that the question has again been raised, but Berger goes much too far when he attempts to deny to the ancients the knowledge and use of the fresco process. The evidence on this point of Vitruvius is quite decisive, as he, and Pliny after him, refer to the process of painting on wet plaster in the most unmistakeable terms. See Note on ‘Fresco Painting, postea, p. 287.
[202]. This passage about the early painters of Flanders occurs just as it stands, with some trifling verbal differences, in Vasari’s first edition of 1550. The best commentary on it is, first, the account of the same artists in Guicciardini’s Descrittione di Tutti i Paesi Bassi, first published at Antwerp in 1567, and next, Vasari’s own notes on divers Flemish artists which he added at the end of the Lives in the second edition of 1568 (Opere, ed. Milanesi, VII, 579 f.). He there made certain additions and corrections from Guicciardini, the most noteworthy of which is the mention of Hubert van Eyck, whom Vasari ignores in this passage of the Introduction, but who is just referred to by Guicciardini at the end of his sentences on the younger brother—‘A pari a pari di Giovanni andava Huberto suo fratello, il quale viveva, e dipingeva continuamente sopra le medesime opere, insieme con esso fratello.’ Vasari however in the notes of 1568 goes much farther than this, and, though he does not call Hubert the elder brother, he seems to ascribe to him personally the supposed ‘invention’—‘Huberto suo fratello, che nel 1510 (sic) mise in luce l’ invenzione e modo di colorire a olio’ (Opere, l.c.). ‘John of Bruges’ is of course Jan van Eyck. Vasari writes of him at the end of the Lives as ‘John Eyck of Bruges.’ Vasari’s statement in this sentence is of great historical importance, for it is the first affirmation of a definite ‘invention’ of oil painting, and the first ascription of this invention to van Eyck. As van Eyck’s own epitaph makes no mention of this, and as oil painting was practised long before his time, Vasari’s statement has naturally been questioned, and on the subject the reader will find a Note at the close of the ‘Introduction’ to Painting, postea, p. 294.