Restoration of Pictures

The conservation of pictures naturally leads us on to their restoration. Picture-restoration, like some other kinds of restoration, often involves injury, often renewal. It is frequently difficult, sometimes impossible, to reestablish the pristine state of the work. The operations involved should never be undertaken by the inexperienced amateur. And picture-restorers themselves are too often artists who have mistaken their profession, or who have been imperfectly trained. Many possess no power or appreciation of accurate draughtsmanship. Look, for illustrations, at those crucial parts, the hands and feet, in 'restored' pictures. Nor have they that exquisite sense of quality in colour and of delicate hues which will enable them to fill up properly actual gaps in a painted surface. Then the pigments they use are too often unsafe, and their vehicles unsatisfactory; so both soon alter, generally becoming darker and yellower. At the same time, the skill of some restorers in the matter of mechanical repairs - parquetting, transferring, relining, etc. - cannot be too highly extolled.

Several manuals of directions for restoring pictures have been given to the world; they are of very unequal value. Some of these tell you nothing, for they are intended merely to advertise the skill of the writers. Others advocate a treatment which may be called heroic, giving you solvents, not only for the discoloured varnish, but for glazings and paints. In reality, no directions can replace experience and skill. The late Max von Petten-kofer's method is one of the best known, but it is very rarely applicable with safety and success. The object of this method is the renewal of the transparency and continuity of the varnish by a process of re-solution in situ. With this intention, the picture is exposed in a closed shallow box to the action of the vapour evolved from moderately strong spirits of wine. This vapour dissolves the mastic on the surface of the picture, forming once more a spirit-mastic varnish. This, on exposure to the air, hardens, and leaves a shining coat of resin. But this resin, being necessarily discoloured and sinking into the cracks of the paint, makes them more prominent, while there is great danger of its being unequally distributed over the surface of the work.

When the varnish of an old picture is practically intact, but the surface is begrimed with soot and dirt, it should not be cleansed by the direct application of water, much less by the use of a solution of soap; but a loaf of household bread, not more than a day old, should be taken, and its crumb broken up into a tin canister furnished with a lid; it is important that no pieces of crust, and no fragments of crumb which have become hard by drying, should be introduced. Then the crumbs should be shaken out, in portions at a time, from the canister on to the varnished surface, and rolled gently thereon by means of the fingers. By repeating this operation until fresh crumbs no longer become discoloured, it is often possible to improve the appearance of a picture very greatly. In any case, it affords a useful preliminary to the removal of the old varnish where such a further step is imperatively required. Such removal is effected by the mechanical process of chafing. A single tear of pure mastic resin is ground or crushed to fine powder, and placed upon some unimportant part of the surface of the picture; but the operation may be begun without the aid of the mastic-powder. A gentle rotatory movement of the ends of the fingers soon reduces the old varnish-layer to powder, which is then removed by means of a soft badger-hair brush, or other suitable means.

The work should be performed in a good light, and great care must be taken not to injure any tender glazings belonging to the painting itself. To ascertain whether the removal of the varnish has been carried far enough, the parts treated may be moistened with distilled water applied on a wad of carded cotton. When the operation is complete, and the surface is quite dry, a new coat of mastic-varnish may be applied, if possible in an artificially dried atmosphere. Sometimes a little dragon's blood, or other warm-coloured resin, is added to the mastic-varnish, in order to prevent the cold and raw look which a picture which has lost its old toned varnish frequently presents. An oil-painting in which no megilp has been used, and which has received, a year after completion, the thinnest possible layer of drying-oil containing a little copal-varnish, and then, after the lapse of a twelvemonth, its final coat of mastic-varnish, cannot be injured by the chafing process just described. And, even under less favourable conditions, it is the only method which can be recommended for general adoption. But it has its risks, and is not easily applicable in the case of pictures where the texture of a coarse canvas, or the grain of a panel, is conspicuously evident on the surface.

To these remarks on the chafing process, we may add that it is sometimes advisable to re-varnish a picture with fresh mastic before commencing to remove the old; a day or two afterwards both layers may be removed together.

The removal of old varnish by the use of solvents is a hazardous, though easy, operation. The liquid usually employed for this purpose is spirits of wine, of about 60° overproof, diluted with one-fourth of its bulk of distilled water. It is applied by means of wads of carded cotton, the action of the solvent being arrested, when necessary, by instantly moistening the spot with spirit of turpentine on another wad, or, in some cases, with linseed-oil. But when mastic megilp has been used as the painting-medium, it also, as well as the pigments associated with it, may be removed by treatment with these solvents. And it must be remembered that some artists introduce layers or touches of water-colours in their oil-pictures; these are almost certain to be affected by spirits of wine. Sometimes further injury to them may be arrested by the application of linseed-oil. Whenever a solvent is used in cleaning a picture, the cotton tufts employed should be examined carefully from time to time, in order to see that no actual pigment has coloured them - that they are stained by nothing but the brown varnish. Other solvents besides those named are sometimes used in cleaning pictures, particularly where hard or oily varnishes have to be removed.

Such solvents are acetone, fusel-oil, amyl-acetate, benzene, chloroform, and solutions of caustic alkalies. Great risk of injury attends their employment - indeed, the application of any kind of solvent is fraught with danger, and should never be attempted by the inexperienced.

The usual plan of filling up actual gaps in the priming or gesso-grounds of old pictures is by means of plaster-of-Paris. When this has set, its surface is levelled by gentle attrition with a cork and dry whitening, or cuttlefish. Great care is needed in order to prevent the pigments surrounding the place from being abraded. I have found asbestos-putty to be an excellent substitute for plaster in many cases; its surface is made smooth and level by means of a painting palette-knife. But it cannot be tinted with water- or tempera-colours; in order to make it match the hues of the neighbouring parts of the picture oil-colours must be used. In any necessary replacements of lost colours in old oil-paintings, it has been recommended to use not oil-colours, but water-colours, as these can always be distinguished from the old work, and, if necessary, removed; this can be done on 'stoppings' of whitening and size, as well as on those of plaster. Tempera-pictures should, I think, be repaired with dry pigments mixed with egg-yolk, as in this case, when the final varnish is applied, a general harmony of effect is produced.

If water-colours are introduced in repairing an oil-painting, the coat of varnish subsequently added is sure to deepen and darken them, unless this change has been allowed for during the progress of the work, by no means an easy thing to manage. When in any kind of repainting oil-paints are used, they should be mixed stiffly with a very little copal-varnish and spirit of turpentine, and should be rather lighter and less yellow in tone than the colours they are intended to match, since darkening and yellowing in some degree, however slight, are sure to occur subsequently.

The cleansing and restoration of paintings executed in fresco require special care. Additions to supply colour which has scaled off are best made in tempera. When a fresco has become grimy by exposure to the smoky air of a city, methylated spirits of wine, applied freely on tufts of carded cotton, removes the tarry and sooty impurities which a previous careful brushing of the painted surface has failed to dislodge. Attempts to clear the clouded portions of an injured fresco by means of distilled water or aërated distilled water are usually attended with but slight success. The films which obscure the surface in such cases sometimes consist of sulphate of lime, produced from the carbonate of lime present by the action of the sulphuric acid occurring in the atmosphere of places where gas and coal are burnt. In getting rid of this somewhat opaque film by means of water, portions of the pigment are commonly removed. When a fresco has been dusted and then cleansed with spirits of wine it should be allowed to dry thoroughly, the lost colours renewed in tempera, and then the whole surface coated with a preparation of hard paraffin-wax. This preparation, which has the consistency of an ointment, is made by melting together 4 parts of hard paraffin-wax (melting-point above 150° F.), 1 part of spirit of turpentine, and 15 parts of toluol.

When cold, this mixture is to be spread uniformly over the painted surface, and then allowed to remain until its volatile constituents have disappeared. Afterwards the paraffin-wax left on the surface is to be melted and driven in by the local application of a moderate heat. By this treatment the dead or matt surface of the fresco is preserved, the obscuring films are rendered translucent, and the picture may, when cleansing is again required, be safely sponged with pure water or weak spirits of wine. If any cloudiness of the surface still persists after the application of the paraffin-wax paste described above, the effect of treatment with the Gambier-Parry medium (see p. 142), largely diluted, may be tried.

The treatment of an injured fresco, in accordance with the plan just outlined, was pursued in the case of Sir Edward Poynter's fresco painted in 1872-73 on the south side of the chancel in St. Stephen's Church, Dulwich. That the work done upon this damaged fresco has been successful may be learnt from the way in which Mr. James Ward wrote in 1909 of the then state of the painting in his book 'Fresco Painting,' on page 30. He there says that this fresco is 'in a perfectly sound condition, and is almost as fresh-looking and bright as when first painted; ... it shows no sign of deterioration; on the contrary, the surface looks, and feels to the touch, more like terra cotta, or of the texture and firmness of biscuit porcelain than anything else one can think of.' Mr. Ward would have come to a very different conclusion as to the permanence of fresco had he seen this painting when I took it in hand some four years before his approval was published!

An example of the treatment of a greatly damaged oil-painting on a plaster ceiling may be here cited. This work, in the Saloon of the Queen's House at Greenwich, was painted between the years 1626 and 1635 by Orazio Gentileschi, a Pisan artist invited over to this country by Inigo Jones. It was reported in 1853 to be 'much damaged'; and fifty years afterwards, when I first examined it, its condition seemed well-nigh hopeless. The plaster ground had swollen, and had broken up and loosened the layer of oil-paint applied to it. This injury was due to the action of atmospheric sulphuric acid upon the calcium carbonate of the plaster. By spraying the whole surface with Gambier-Parry's spirit fresco medium considerably diluted, the coloured flakes which were ready to fall were secured in position, and then the lost portions were replaced by pigments ground in the same medium. These operations were carried out between the years 1907 and 1909. In cases of such serious damage as this of Gentileschi's ceiling, further treatments are necessary, as the injury to the plaster is a continuing one.