It was stated at the beginning of the present article that what the art of picture restoration has lacked throughout the centuries is a sound tradition. Really encouraging results have been achieved, but it must be clearly understood that restoration is a vocation rather than a trade. In order to practise it, it is first necessary to be a real painter, and in the second place to make a constant study of the practical methods which the old masters used to achieve their artistic aims. However much their works are searched, the number of discoveries which have been made remains limited. At any rate a study of this kind will show that the one supreme quality which a restorer should possess, if he is to try his hand on great works of art, is the gift of respect.
(J. G. G.) Restoration and Preservation: L. B. Guy-ton de Morveaux and others, Rapport sur la restauration du tableau de Raphael connu sous le nom de la Vierge de Foligno (1802) ; Horsin-Deon, De la conserva tion et de la restauration des tableaux (1851) ; U. Forni, Manuale del pittore restauratore (Florence, i866) ; 0. E. Ris-Paquot, Guide pratique du restaurateur amateur de tableaux (189o) ; C. Dalbon, Traite technique et raisonne de la restauration des tableaux (1898) ; G. Meusnier, De l'entretien et de la restauration des tableaux (1909) ; A. Jehn, Chromatisme revivifie: Transparence obtenue tout en conser vant les anciens vernis et les patines (19n).
The existence of countless fraudulent paintings is generally acknowledged. Apart from the more obvious cases which have reached law courts and publication, there are numerous references in the note-books of artists to the making of copies which, although legitimate in their original purpose, have become fraudu lent in the hands of opportunists. In a similar way the work of pupils, supervised or corrected by a master, and put out originally as shop work, has been made in later times to pass for the work of the master. One therefore must distinguish between the several types of forgery. The work deliberately manufactured at first hand in imitation of older work constitutes an important first class—sometimes most difficult to detect. Next to this are the groups dealing with the transformation of something already existent into something else, such as the refinishing of a crude school piece in the master's manner, or the remounting of frag ments of an old picture to serve as the skeleton of a finished work, or even the mounting of an overpainted chromolithograph on a decayed piece of wood or canvas to imitate the appearance of an old picture. Perhaps there should be a separate classification for
some kind of repair work on damaged pictures; in this group the forgery consists in falsifying what remains of the original. But in all kinds, the forgery may be considered as a substitution, whether of colour, or brushwork, of subject, or of spirit and con ception, with or without the intention to deceive. In order to guard against this imposition the expert must be able to recognize the clues which point to its existence.
The material differences between the true and the false suggest chemical and physical analysis; the spiritual differences suggest psychological and historical analysis. In effect the expert makes use of any means that suggest themselves to him. Chemical tests may determine the composition of colours, of which the date of discovery is known. (See PAINT, CHEMISTRY.) The presence of Prussian blue, for example, in a painting supposedly of the I 5th or even the i 7th century is absolute evidence of forgery or repaint ing. The needle test, mainly of anecdotal value, shows whether or not the oil in an oil painting has hardened; if the paint cracks when the needle is inserted, the oil has solidified; if the needle's hole is round and unbroken at the edges, the oil medium is prob ably less than 3o years old, according to some, or less than 5o years old, according to others. A strong magnifying glass or low powered microscope may determine whether apparent cracks are natural or have been drawn in with a sharp point. Polarized light has been suggested as a means for seeing beneath the dirty varnish, glaze and repaints in certain types of painting.
By far the most common method, however, if it is properly a method, for determining forgery is by means of the emotional sen sitiveness which develops from long familiarity with works of art. Critics, necessarily in sympathy with their subject, mark slight deviations in spirit, form and style which indicate the presence of something alien—a forgery or imitation of a known model. Detec tion of such deviations presupposes, of course, a complete knowl edge of the art imitated and a range of information wide enough to develop what are at first merely suspicions into proofs, demon strated by whatever historical and inferential facts can be found to support the primary emotional one. The critic's hypothesis ordinarily is derived from emotional experience, and the proof from technical data.