Pictures, Prints, and Frames.—Pictures.—(a) Remove the works from their frames, and first of all examine the surface of each separately and with care. Then, if there are no cobweb cracks, no cockled-up edges of bits of paint likely to peel off, and no unburst bubbles of colour, take an old soft cloth, and some white of egg, and wash the surface, a square inch at a time, with a spiral motion of the hand, not pressing too heavily. If there is much dirt, make a basin of bread, treacle, and new milk with a trifle of turpentine in it, and wash with soft flannel and sponge; after, use white of egg. If mildew from damp walls has attacked the canvas, and even the surface, let a committee of artists be called; there are so many varieties of this form of injury, it is well to understand the particular case. If coal gas, foul air, or other pollution is suspected of having injured the varnish, an artist chemist, learned in varnishes of the different schools, must prescribe; but if the surface is injured, or the colour scales off, no amateur can repair the crack; and in every case, before returning the well-cleaned and well-rubbed surfaces to their frames, let good plate glass be securely fastened over each to prevent future injury.
(b) Pictures may be cleaned by rubbing the thumb over the painting moistened with saliva, or by a raw potato cut in half and rubbed evenly over the picture.
(c) Dissolve a little common soda in urine, then add a grated potato and a little salt; well rub this over the paintings till clean. Wash off in spring water, and dry with a clean cloth.
(d) First rub the picture well with good whisky, which will make the varnish come off in froth, then wash well with cold water, and when dry varnish again; this will restore the picture to its original colour unless very old. Keep the picture covered from dust till the varnish is dry.
(e) The painting is first removed from the frame, and the dust and smoke brushed off with a pencil or feather. After this it is washed with a sponge dipped in well water. It is next covered with a thick layer of soap; shaving soap is the best for the purpose, because it remains moist and does not dry on. After the soap has been on 8 or 10 minutes it is all washed off with a strong brush or pencil, adding a little water if necessary. The soap that still adheres is rinsed off sufficiently with water, and the picture left to dry. When completely dry, it is further cleansed with nitro-benzol—also known as nitro-benzine, artificial oil of bitter almonds, or essence of mirbane. It is a yellowish oily, poisonous liquid, with a powerful smell of bitter almonds. It is formed when coal-tar benzol is mixed with fuming or concentrated nitric acid under suitable precautions. The nitro-benzol is poured into a dish, and a clean linen rag is dipped in it, and passed over the painting. This quickly removes all the adherent dirt. This linen rag must be frequently exchanged for a clean one. When the rag remains clean after going over it repeatedly, the cleansing is finished. If the colours look dull after going over it the last time and letting it dry, it is given a thin coat of the finest olive oil, and after a while must be varnished with a good, quickly-drying varnish. (Von Bibra.)
(f) The picture had better first be sponged with cold water and allowed to dry, then apply solution of hydrogen peroxide with a clean sponge in successive lines, not going over the same surface twice; again allow to dry. If the solution is sufficiently strong, the painting is now tolerably clean; if not, a second or third application is necessary. Peroxide of hydrogen, hydroxyl, or hydrogen di-oxide (H2O2), owing to the readiness to part with half its combining weight of oxygen, is a powerful bleaching agent; but the way in which it serves to clean oil paintings is accounted for thus:—Sulphuretted hydrogen, which is present in the atmosphere, especially in the neighbourhood of towns, attacks the lead in the paint and forms lead sulphide, which is readily soluble in peroxide of hydrogen, water and lead sulphate being the result; thus
PbS + 4H2O2 = PbSO4 + 4H2O (J. T. C. Williams.)
Prints.—(a) Presuming these to be mounted, proceed in the following manner. Cut a stale loaf in half, with a perfectly clean knife; pare the crust away from the edges. Place them on a flat table, and rubbing the surface with the fresh-cut bread, in circular sweeps, lightly but firmly performed, will remove all superficial markings. Soak the prints for a short time in a dilute solution of hydrochloric acid, say 1 part acid to 100 of water, and then remove them into a vessel containing a sufficient quantity of clear chloride of lime water to cover them. Leave them here until bleached to the desired point. Remove, rinse well by allowing to stand an hour in a pan in which a constant stream of water is allowed to flow, and finally dry off by spreading on clean cloths. Perhaps may require ironing between two sheets of clean paper.
(b) Put on a smooth board, cover it thinly with common salt finely pounded; squeeze lemon juice upon the salt so as to dissolve a considerable proportion of it; elevate one end of the board, so that it may form an angle of about 45° or 50° with the horizon. Pour on boiling water from a tea-kettle until the salt and lemon-juice be all washed off; the engraving will then be perfectly clean, and free from stains. It must be dried on the board, or on some smooth surface, gradually. If dried by the fire or the sun it will be tinged with a yellow colour.
(c) Hydrochloric acid, oxalic acid, or eau de Javelle may be employed, weakened by water. After the leaves (if it be a book) have by this means been whitened, they must be bathed again in a solution of soda sulphate, which will remove all the chlorine, and leave the pages white and clean. They will, however, have lost all firmness of texture, owing to the removal of the size from the paper. It will, therefore, be advisable to give a bath of gelatine and alum made with boiling water, to which may be added a little tobacco, or any other simple substance to restore the tint of the now too white paper.