Where a picture is painted by glazing, especially where varnish comes in instead of body, it is apt to crack or thread like a cobweb. In time these divisions will scale off in flakes. Wax dissolved in turpentine is used for the light cracks. Scaling must be treated by careful softening with oil and pressing down a warm iron. The surface must, previous to ironing, be covered with chalked paper.
It sometimes happens that a picture has been painted over, and I have seen a very distinguished restorer in such case succeed in removing the outer coat. This requires great knowledge of the chemical properties of the paint; also of solvents, and the different methods of scraping, absorbing, &c. Still, it can be learned with patience. Extraordinary results have been thus obtained. It has often happened that men with little or no knowledge of painting have fancied themselves capable of “repairing” very valuable pictures, and so smeared them over to utter ruin.
Before attempting to retouch an old picture, let the restorer make a copy of it. If he can do this very well he is qualified for his work, and not otherwise. The fraternity of picture-cleaners and menders may protest against this; but the vast amount—I may say the vast proportion, meaning the majority—of good pictures spoiled by bad retouching confirms the truth of my assertion.
It is worth remarking in this connection that very few amateurs, æsthetes, or “connoisseurs,” so called, appreciate the value of mere technique or practical work in art. They “swarm for the ideal,” and that is all. The great masters were wiser than this. It would do much good if very generous prizes on a large scale were to be paid annually for copies of great pictures. And I would have rewards given specially for pictures painted with colours prepared by the artists themselves from chemically pure and unalterable materials, according to the ancient recipes. I would like to see a society formed of artists who would produce such work. It would certainly find buyers—in time.
There are to be found in most curiosity shops in Italy panel pictures of the fourteenth century, earlier or later, with gold grounds, which can be had of all prices, from a very few francs upward. They are without name and of no great artistic merit, but very curious and interesting indeed as ancient relics painted “before oil,” and as inspired with the spirit of the Middle Ages. These generally require restoration. They were painted on wood of all kinds, very often on deal. The surface was covered with a thin coat of gesso or plaster of Paris, mixed with the white of egg, and on this the gilding and paint were applied. The latter was in white of egg and fig-juice, or encaustic—that is, wax and white of egg, which is the most ancient and durable method known; so much so that long after every oil-painting ever executed (if left to itself) will have disappeared, the ancient Egyptian, Roman, or Middle Ages pictures will be as fresh as if made yesterday.
If a panel be warped or bent, it is straightened by damping the concave side, and screwing to it crosspieces. If the ground be scaled away, supply it with powdered plaster of Paris mixed with gum-water. The repainting can be executed with water-colours mixed with white of egg, gouache, or even oil in small quantities, which should be rather rubbed in or glazed than painted in body.
A common panel picture of the fourteenth and fifteenth century, painted with white of egg, can be well enough restored with water-colour, or gouache, and then varnished. But the colour with gouache medium will not hold well, except on the gesso-ground. It is apt to scale off from any smooth, hard surface. Therefore it is difficult to restore them by painting on the old hard glaze. Most of the mediums which are sold to heighten water-colours—e.g., Winsor & Newton’s glass medium—will cause the colour to adhere.
A GROUND FOR WAX-PAINTING ON POROUS SUBSTANCES was made as follows:—
| White wax | 10 |
| Resin | 5 |
| Essence of turpentine | 40 |
Melt the wax in a bain-marie, pass the solution through a linen strainer, and lay it on in successive coats on a wall which is first heated by a hand-furnace or brazier. To close holes in the wall use a putty made of wax, gum-animé, resin, and whiting.