In Europe the art of repairing and revarnishing, or, as it is called, "restoring" pictures, is quite a business; and as this country grows, the business will no doubt become more general and lucrative. In its best phases the art of restoring pictures demands great skill and special taste; but there are certain cases which may be met by mere routine system. Some of the ablest scientific men have devoted their attention to the improvement of the methods in actual use; and many of their suggestions are well worthy of attention by the practical man.
Valuable paintings should be kept in a dry place, and one free from foul air. Dampness soon destroys the canvas or wood upon which the picture maybe painted; and the foul emanations from stables, sinks, graveyards, etc., soon destroy the finer colors, owing to the action of the sulphuretted hydrogen and carbonic acid. Hence churches, vaults, stables, and similar places, are entirely unfit for storing paintings.
The darkening of the lights in oil paintings may be quickly changed by the application of the solution of peroxide of hydrogen, - a compound which is now found in market under the name of "Golden Bleaching Liquid." Under the action of this liquid the sulphides are at once converted into sulphates.
Paintings which have been injured may often be restored by the exercise of a little skill. In such cases the following directions will prove useful.
When by the continued pressure of some hard body the canvas presents either a concavity or convexity in a portion of its surface, it must be well wet in that part, and left gradually to dry in some cool place, keeping it constantly under pressure.
When the color has separated from the priming, whilst the priming still remains firm, the swollen and detached part is first rubbed over with the same paste which will be presently mentioned as used for lining. Then, with a pin or needle, little holes are punctured in the part, and more paste rubbed over these holes with a pencil, and worked about so that it shall pass through them. The surface is then wiped clean, and over the spot a pencil is passed that has been dipped into linseed-oil. This serves to soften it. A warm iron is then passed rapidly over the raised surface,which attaches itself to the priming as before. Should it bo necessary to line the canvas with a new one, it should be done previously.
When a canvas is broken, rent, or perforated in any part, the piece of canvas that is used to repair the damage is dipped into melted wax, and applied the moment it is taken out, warm as it is, to the part, which has been previously brought together as well as possible, and also saturated with the wax. With great care you flatten down the piece; so that as the wax chills and concretes, the parts adhere and are kept smooth. The whole being made perfectly level, and the excess of the wax removed, a mastic made of white lead mixed with starch is applied; for oil-color does not adhere well to wax. The white is afterwards colored thin, or by washes, according to the tone of the surrounding parts, and repainted.
When the priming of a canvas has become detached, or the cloth is so old as to need sustaining, it is customary to line the picture. But if the canvas is greatly injured, the painting itself is transferred to a new subjectile. In order to render the old canvas and the color softer and more manageable, expose the picture for several days to damp When all is ready, the first step is to fasten, by a thin flour-paste, white paper over the whole painted side of the picture, to prevent the colors scaling off. Having a new canvas duly stretched on a strong frame, a uniform coat of well-boiled paste, made of rye-flour with a clove of garlic, is spread nicely over it by means of a large brush. With dispatch, yet care, a coat of the same paste is spread likewise on the back of the picture. The latter is then laid upon the new cloth, the two pasted sides of course together. With a ball of linen the usual rubbing is given with a strong hand, beginning at the center, and passing to the edges, which must be carefully kept in place the while.
In this way the air is expelled, which remaining would cause blisters.
The picture thus lined is then placed upon a smooth table, the painted side down, and the back of the new canvas is rubbed over boldly with any suitable smoothing instrument, such as is used for linen, paper, or the like; and a warm iron is then passed over the picture, having on the other side a board to resist the pressure. The paste being heated by this iron, penetrates on the side of the picture, and fixes still more firmly the painting, while on the other side the redundant part of the paste escapes through the tissue of the new cloth, so that there remains everywhere an equal thickness. The iron must not be too hot; and before applying it several sheets of paper should be interposed between it and the paper that was at first pasted on the painting, and which would not be sufficient.
When the lined picture is sufficiently dry the paper last mentioned is damped, by passing over it a sponge moistened with tepid water. It soon detaches, and with it is removed the paste that secured it to the picture. All that remains is to clean the painting, and where needed to restore it.
The above operation will not, of course, be attempted by the amateur, except for experiment upon some picture of little worth; for even practised hands frequently injure what they were employed to preserve.