Part 2

The methods so far described of detecting forgeries may well be as old as the practice of forgery itself. Certainly, they form the basis of all investigations of which we have records, as well as of those made today. Their efficiency, however, has been immensely increased by the development of scientific methods of investigation. The first great step forward came with the use of photography, which permitted comparison of suspicious objects with genuine examples in a way hitherto impossible. Next came the application of various scientific techniques to the analysis of the physical constitution of an object. So spectacular have been the results in some cases as to create a blind faith in such methods of investigation, almost as though a piece of scientific apparatus were an oracle which when consulted would answer “Yes” or “No” to the question of whether an object is genuine. The limits of scientific investigation are, however, clearly marked. This method is solely concerned with the physical make-up of an object, and is completely indifferent as to who made it, when and where it was made, and why it was made. All that it does is to make possible the discovery of physical facts bearing upon these matters, which have to be observed and interpreted by human minds and used as the basis for human judgments.

The scientific procedures with which we are concerned here fall into two main groups. Of these, one includes various techniques for extending the range of human vision. The simplest is examination by microscope, which enables characteristics of a surface to be seen that would otherwise be invisible, so that, for example, painted cracks or cracks artificially induced can be distinguished from crackle due to age. With the microscope, too, evidence of removals and additions can be obtained, such as the manipulation of signatures and inscriptions, or the presence of repaint or artificial patina; while the structure of pigments, stone, etc., can be ascertained, as a step toward their identification. More elaborate is examination under various rays of the spectrum, to which the human eye is not sensitive but whose results can be recorded. The best known of these is X-ray, which penetrates certain substances but is held up in different degrees by others, especially metals, so that a photographic film behind an object will record a map of such substances in an object, thus revealing much that is below the surface. On the other hand, ultra-violet rays falling on a surface cause fluorescence, which varies according to substance and texture, so that additions to the surface may be revealed. Infra-red rays, in contrast, penetrate the surface, and are reflected back from the layers beneath, so that a photograph taken by infra-red light may reveal something concealed from the eye, which X-ray may not pick up.

The second group of investigatory methods includes various means of analyzing the materials present in an object. The most familiar is chemical analysis; but this is being supplemented and to some extent displaced by spectrographic analysis, with its recent extension in the use of X-ray diffraction. By these means, it is possible to detect even minute traces of substances whose presence or absence may be decisive in settling the date or provenance of a material. Some recent applications of quantitative analysis have proved helpful in ascertaining the date of objects. One of these techniques, determination of the extent of fluorination, was used to prove that the jawbone of the Piltdown skull was a modern forgery; while another, based on the amount of radio-active carbon present, which is known to decay at a certain rate, is still in course of development, but promises to be most useful.

Thus, a formidable group of weapons are available against the forger. To be effective, however, the significance of the facts they bring to light must be understood. Decisive proof that an object is not of the period or by the hand to which it is attributed comes only through the discovery of facts which are not only inconsistent with the attribution but cannot be explained except by assuming that the attribution is wrong. For instance, the body of a work may contain a substance unknown at its ostensible date. Modern nails inside a piece of wood sculpture said to be of the fourteenth century; cobalt, unknown as a pigment until the early nineteenth century, in a painting attributed to Velázquez; and titanium white, a twentieth-century invention, in a portrait labelled fifteenth-century Florentine—these are all good evidence that the object is not what it is held out to be.

Moreover, the facts discovered always have to be controlled by reference to established standards. Structure revealed by microscopic examination must be compared with that of known substances; chemical and spectrographic analysis has to be checked by reference to a codified series of earlier tests; crackle on a surface can only be labelled as false if the nature of genuine crackle is known; and the reading of whatever is discovered by X-ray, ultra-violet, or infra-red rays calls for comparison with verified results of previous examinations. The facts yielded by one method of investigation may by themselves not be sufficient evidence of forgery; if, however, they can be joined with the results of other methods, all pointing in the same direction, a strong case can be built up. As in a court of law, this, rather than production of a single dramatic and decisive piece of evidence, is what usually happens.

It might be thought that the combination of expert and scientist would leave the forger with his occupation gone. On the contrary, he continues to flourish. In the face of the expert, he discards the clumsy copy and the inept certificate, utilizing the improved methods of photography and reproduction and the increasing flood of learned works, to help save him from anachronisms and inherent contradictions in his work. The scientist he meets either by concentrating in fields where scientific methods of inquiry are relatively helpless, or by himself going to school with the scientist. The results of recent scientific work have put at his disposal much knowledge of what to do, what to avoid, and how to baffle certain types of investigation. Moreover, he has even taken over certain procedures worked out by scientists, such as those for hastening the effect of time, and has applied them to his own problems; cases are known of forgeries having been submitted, through innocent hands, for scientific investigation, to find out whether they will survive the ordeal, and if not, what are the mistakes to be avoided in the future.

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One question is often asked in connection with forgeries: Why should a once-admired object be disregarded or condemned on being proved a forgery, seeing that it is still the same object? One reason is human snobbery; another, and more important, is that when an object is proved to be a forgery, it is to us no longer the same object that it was. After the discovery, human knowledge about the positive and negative qualities of the object has increased, and a new judgment has to be made upon it. Exactly the same thing happens with a genuine work. As familiarity with it grows, it becomes another thing to the spectator’s eyes and mind, and so it may rise or fall in his esteem. Conceivably, the characteristics which proclaim something to be a forgery might, when discovered, cause it to be more highly regarded; but that kind of forgery is not yet known, though it may perhaps exist.

William George Constable was born in Derby, England, in 1887 and educated at Cambridge University and the Slade School of the University of London. He was formerly Assistant Director of the National Gallery, London; Director of the Courtauld Institute (University of London); and Slade Professor of Fine Art at Cambridge University. Since 1938, he has been Curator of Paintings at the Museum of Fine Arts, Boston.

The author of numerous books and magazine articles, Mr. Constable has devoted himself particularly to the study of English and Italian paintings and drawings. This is reflected in his more recent publications: _Venetian Painting_ (1950); a monograph on the English artist Richard Wilson (1953); and _The Painter’s Workshop_ (1954).

Transcriber’s Notes

—Silently corrected a few typos.

—Retained publication information from the printed edition: this eBook is public-domain in the country of publication.

—In the text versions only, text in italics is delimited by _underscores_.