Majolica consists generally of terra-cotta covered with a glaze. A glaze is a fusible substance, we may say a kind of glass, mixed with colouring matter, which is at the same time a protection and an ornament. Enamel is glass in fine powder melted, used generally on metal or by itself. The base of the paint is a substance fusible by heat which is mixed with colours also fusible. Therefore when the painting is submitted to heat it melts, adheres, and is permanent. Glazing, enamelling, and china painting are essentially the same.
Terra-cotta is not difficult to mend. I can best illustrate this by an example. A friend once gave me a terra-cotta vase from the Pyramid of Cholula, in Mexico. These are supposed to be of very great antiquity. This contained a fragment of pottery, probably a sacred relic of ruder style, and I suppose of far earlier times. The vase, however, had been broken to fragments, and the owner was about to throw it away as worthless. I begged it of him. Firstly, I put the principal pieces together, using, to make them adhere, glue with nitric acid. For finer work I should have used Turkish cement or the best gum-mastic dissolved in spirit or fish glue. Piece by piece with care I reconstructed the whole.
There was wanting, however, one piece about three inches square. I pasted with great care a piece of paper inside the vase for a back, and then poured on it plaster of Paris liquefied with water. To make this set hard, the plaster or gesso should be made with burnt alum-water and dissolved gum-arabic. This exactly supplied the missing piece.
When it was finished, I filled in all the broken edges and other cavities with the plaster-paste, which set even harder than the terra-cotta. The outer colour of the vase was of reddish rusty black. I painted the whole over with a corresponding colour; that is to say, I rubbed it in by thumb, which is very different from mere painting. By cementing and rubbing I so restored the whole that the repair was hardly perceptible. This process is carried to great perfection in Italy with broken Etruscan ware.
I may here remark as regards rubbing in oil or water colours, that it is little known or practised, but it is of great value in restoration when we wish to produce certain curious antique-looking effects. I once knew in Rome an artist who had bought for a trifle an old carved baule or chest. By rubbing in with care on it Naples yellow and brown shades, and subsequent friction, he had made it look strangely like old ivory. Mere painting, however skilfully performed, would not have given it its antique ivory look. The same artist had purchased one or two common, large, yellowish terra-cotta wine-jars. He drew on them classical figures, cut out the outlines a little with chisel and file, and smoothing the figures with sandpaper, also ivoried the whole by rubbing in colour. This was but a few hours’ work, yet the effect was startling. What had cost but a few francs would have sold for hundreds. I should add that with the aid of fine retouching flexible varnish this process could be very much facilitated. Any one who can draw or paint at all can try this experiment on any old piece of wood-carving, or on a common yellow coarse earthenware. Smooth the latter first with sandpaper, then rub in the colours. The same is applicable to old carving in marble.
All of these devices are of use to the restorer. As regards restoration of terra-cotta, the field is wide and profitable. Not only in Italy, but even in London, we may find for sale broken Etruscan vases or similar objects for a trifle, which are extremely easy to restore. These are generally of red or light yellow clay baked. If you have, let us say, a vase fractured, obtain clay of the same colour—if you cannot readily get it, take pipeclay—and colour it with a strong infusion of red or yellow, though this is not necessary if the exterior is black. Mix the clay well with glue or gum-arabic and alum-water, supply the missing portions, and let them harden. With a little care and practice, remarkable restorations may thus be made. I may here add that with this composition, bottles, decanters, and cups can be coated, which, when painted or rubbed in, exactly resemble Etruscan or other ancient pottery. To prevent cracking, they should first be painted with thick, coarse oil paint mixed with sand or umber, which forms a ground. Let it dry—the longer the better—and then rub in, thinly, the gum and clay. There is another composition of blanc d’Espagne, or whiting, and silicate of soda, which sets even harder, but which is a little more difficult at first to work, which may be used for such restoration. This can be directly painted on glass for a ground.
Majolica or Faïence can generally be sufficiently well mended with acidulated glue, but as the latter often communicates a dark stain, it is better to use for fine ware, or any which is to be used, the so-called Turkish cement. The best quality of this is made of the finest quality of gum-mastic dissolved in spirit. It is so tenacious that in the East gems are frequently directly attached by means of it to metal, and they will often break sooner than separate from it. Most chemists have for sale, or will prepare for you, some form of it. The silicate of potash and whiting can also be supplied by chemists; they should be mixed with great care, so as to form a medium paste, and then used rapidly and with skill, because this cement hardens very quickly. It is, however, a very powerful binder, and sets as hard as glass.
Having put together and cemented the broken pieces of a cup or vase, they must be kept in place till the cement dries. This is effected by means of many contrivances, regarding which the operator must employ some original inventiveness. Firstly, the pieces can often be simply tied, or attached by pieces of tape, or parchment, or paper glued on. In other cases india-rubber bands are useful. Again, bits of wood, or sticks and wires, are the things useful. A bed of wax is generally a sure guard. It is best to do this with great care, and not impatiently rely on holding the pieces together with the fingers till they stick. This is often the most difficult part of the whole operation; therefore it should be done well and deliberately. And here it may be remarked that, as in surgery, the most complicated cases of fracture may be studied out and adjusted; for which reason I dare say that skilful surgeons would be good menders of crockery, just as good astronomers are always good riflemen.
When the broken pieces are adjusted and all is dry, there remain the chips, hollows, ragged edges, and “hairs,” as the French call them, or lines of juncture, to be filled and smoothed. This is done with the cement which you employ, according to the quality of the material, either plaster and gum-arabic, silicate and whiting, or powdered chalk. Some experts succeed with white of an egg and finely powdered quicklime, which holds firmly, but which requires practice to amalgamate. Fill the cavities carefully, pressing the cement well in, as the Romans did, with a stick or point. When all is smooth, paint over the blank spaces and varnish with Sohnée, No. 3, or with a slight coating of silicate. Fine copal varnish is rather tougher or less brittle.
The most thorough process of all is to unite the fragments with a vitreous or metallic flux, such as the silicate—there are several of these—and then have the work baked or fired. It can then be painted with porcelain colours under glaze, and fired again. As this is very delicate, difficult, and expensive, few amateurs will care to try it. It is, however, perfect, and by means of it the most complete reparation can be effected. The Japanese do this simply with the blow-pipe, by means of which they fix enamel powders even on wood. This use of the pipe is also difficult, but the ancient Romans are said to have employed the process with most minor work. As a thread of glass will melt in a candle, and as fine-glass powder is equally fusible, it can be understood that under the flame of a blow-pipe the latter can often be melted so as to avail in restoration.