Forgers and Forgeries

by W. G. Constable

ABOVE: An imitation of the work of John Constable, distinguished from an original (BELOW) by its coarse handling and mistakes in topography.

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.

ABOVE: A forgery of a painting by Utrillo adapted from a genuine example, compared with another genuine picture (BELOW). Note the clumsy handling of paint and drawing in the forgery.

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.