The Chemistry of Paints and Painting is a free textbook on chemical aspects of painting. See the editorial for more information....

Painting Grounds and Colors

The study of old pictures, with the view of discovering the causes of the physical and chemical changes which have taken place in them, is fraught with interest. The material on which they are executed, the medium employed, the pigments which can be identified, and the varnish which has been applied to the surface, all these matters demand attention. The dates of the various works examined, the countries in which they have been produced, the conditions under which they have been preserved, and the treatment to which they have been subjected, constitute elements in the investigation which, whenever possible, should be kept in view. But the adequate treatment of this extensive subject requires not a brief chapter, but a whole volume. And then our materials, though in some directions most abundant, are in great measure inaccessible. We must confine our attention to such specimens as are shown in our public galleries. Even then we find ourselves hampered by the impossibility of making the thorough investigation which is desirable, and by the too frequent absence of certain important data.

In the present chapter we limit ourselves to some general remarks, and to a few brief observations upon a certain number of pictures in the National Gallery, the National Portrait Gallery, and the Victoria and Albert Museum; and our selection will be confined to paintings in oil, tempera, and water-colour, as the available works in fresco in England are too few and too fragmentary to furnish the information for which we are seeking.

It will hardly be necessary, with respect to changes in painting-grounds, to do more than refer the reader to what has been already said on this subject in Part I. of the present work. The causes of the decay of panels and of the convexity which their painted surface shows in so many cases have been already discussed. The disruption of the ground and of the superposed layer of paint consequent upon this convexity needs no further explanation. The staining of the white priming which has been laid on certain kinds of wood has been traced to dark-coloured exudations of soluble organic matters. The grain of some kinds of wood, notably of oak in pictures of the Dutch and Flemish schools, often becomes painfully conspicuous in course of time, and gives to the surface-cracks a peculiar character. The microscopic structure of certain woods and the peculiar distribution of their histological constituents serve to explain these appearances. The causes of the decay and cracking of gesso-grounds in which size has been used, and the injurious mechanical and chemical alterations which paper and primed canvas may exhibit, have been already touched upon. The other conspicuous changes which may be observed in old pictures are connected with the medium, the pigments, or the varnish.

All these matters have been referred to in Parts II. and III., yet there are three points on which further discussion may not be out of place. I refer to the number and character of the pigments used in early works, to the manipulation of the paint, and to the employment of white lead. Now, the pigments to which the earlier painters were restricted were not only few in number, but were mainly of mineral origin. At the first glance one sees that the Italian artists of the thirteenth century, and of the first half of the fourteenth, worked almost exclusively in natural inorganic pigments, two of which stand out in their works in startling prominence, namely, vermilion and ultramarine; and their pigments were nearly all opaque or semi-opaque. The absence of any pure and brilliant yellow, opaque or transparent, from their pictures is another noticeable characteristic. In the works of Jan van Eyck and Rogier van der Weyden, and in those of many of the Italian painters of the fifteenth century, the range of colours is more extensive. Pigments which could not be used in tempera or size, or which were semi-opaque when employed with these vehicles, gave great richness and variety to their works in oil.

This tendency to press into the service of pictorial art other coloured materials besides those of mineral origin, namely, animal and vegetable pigments in considerable variety, became more marked as time went on. And during the nineteenth century the progress of synthetical chemistry placed at the disposal of the picture-maker a long series of pigments - good, bad, and indifferent, - so that the chances of introducing dangerous and fugitive colours have been enormously increased. It is to this increase in the number of pigments, and to their greatly extended range of composition, rather than to their mode of preparation, that one should attribute in great part the frequent deterioration of modern paintings.

But the second point to which reference has been made is concerned with the mode of laying on colours. The exquisitely minute and careful manipulation of Jan van Eyck, of Fra Giovanni Angelico, of Hans Memlinc, of Gerard Dou, of Gerard Terborch, and of many another old master, could not have been hurried. It was solid but smooth; the paints hardened gradually into one organic whole. And we could name several oil-painters of the eighteenth century, and even of the present day, whose work is executed in the same safe manner, and which, were it not for the occasional introduction of dubious materials, would be sure to remain sound for hundreds of years, provided, of course, that the painting-ground be satisfactory. But this careful mode of painting does not suit the temperament, nor is it capable of expressing the ideas of many artists. The thick impasto and loaded colour, the effective brush-work, the juicy pencil, and the dashing haste of several painters often prove to be elements of danger.

Last Update: 2011-01-23