Part 3

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.

CROCKERY, OR FAÏENCE, AND PORCELAIN.--“Crockery,” by which we commonly understand such ware as that of the blue willow plates, is far superior to terra-cotta, since its _core_ or basis is thin, and very hard, and its gloss of a different description, and more incorporated with the body; or it is of a single superior body.

PORCELAIN differs entirely from the other two kinds of fictile ware, being an elaborate mineralogical compound, its base being _kaolin_, a friable, white, earthy substance, requiring great care in its preparation, and _petunse_, or feldspar, which is united with the _kaolin_. The result is a very delicate and beautiful diaphanous ware, or one through which light passes to a limited degree. Both crockery and porcelain are far more difficult to mend, owing to the impossibility--particularly with the latter--of making fractures disappear.

The first and most simple process of mending both kinds of ware is to make small holes with a drill along the edges of the fracture, and then, adjusting the fragments, bind them together with wire. M. RIS-PAQUOT claims that “the honour of this discovery belongs properly to a humble and modest workman named DELILLE, of the little village of Montjoye, in Normandy.” But the archæologist will say of this claim, as the English judge did of a similar one, that the plaintiff might as well apply for a patent for having discovered the art of mixing brandy with water, since there was probably never yet a savage who had wire, or even string, who did not know enough to mend broken calabashes, jars, and pipes by this solid method of sewing. From the time when large earthen punch-bowls were first used in Europe, we find them mended with silver wire. It is needless to devote whole pages with illustrations, as M. RIS-PAQUOT has done, to show how to effect such mending. The holes are made with either a bore or hand drill, such as can be bought in every tool shop. If the reader will obtain one and experiment with it on any penny plate or broken fragment, he will soon master all the mystery. The wire is made fast by a turn with a pair of nippers or pincers. Before fastening, wash the edges of the ware with white of egg in which a very little whiting, or finely powdered lime or plaster of Paris, has been mixed.

I may here observe that the wire for china-drilling should be half round, or flat on one side. To prepare this, take brass wire, say a length of about two feet, and, holding an old knife, draw the wire firmly and steadily against it.

There are endless cements for sale by chemists, all warranted perfect, to mend glass and china, and most of them do indeed answer the purpose very well, for nature has given us not a few materials wherewith to repair accidents. Thus, even boiling in milk will often suffice to reunite broken edges. But I believe that of all, the Turkish cement already described, which is made of gum MASTIC (a term improperly applied in France to putty, by Americans to lime-plaster on houses, and by Levantines to spirit with resin in it), is the most adhesive and resistant to heat, cold, or moisture.

The art of mending does not consist so much of knowing what to use for an ADHESIVE (since, as I have said, every chemist’s shop abounds in these) as in skill and tact with which fragments are brought and kept together, missing portions supplied, and in knowing the substance with which to fill a blank. There are cases in which, when a hole has been knocked in a china or glass plate, it can be drilled out round, and a disc of the same substance or colour, or even of another, inserted. This is almost an art by itself, and by means of it very singular and puzzling effects may be introduced; as, for instance, when a number of holes are drilled in a white china plate and then filled with discs of coloured china, agate, coral, &c. In the East, turquoise and coral beads are often thus set into porcelain, as well as wood. The mastic or acidulated glue is used to make the objects inserted hold firmly.

As the smoker, when he breaks his pipe across the stem, has it repaired with a short silver slide or tube, so when a china jar is broken across the neck, the reparation can be concealed by a silver collar, which is sometimes a great improvement; as, for instance, when the head of a china dog, or even of a china man, is taken off. But in a great many cases, or in all where this kind of concealment is advisable, it may be made, like Cæsar’s wife, beyond suspicion, by making the collar or concealing ornament, or leaf or flower, of silicate and whiting so as to resemble the ware itself, which can be done very nicely.

SILICATE OF SODA is sometimes sold in the form of a dry solid, which is placed in a little vinegar, and warmed. When dissolved it can be used _ad libitum_. It is often used as a glaze for stone.

There is a curious old story about mending broken crockery by means of magic--or rather by deceit--which, though not of a practical nature, is at least amusing. It is partially told in a book published about 1670, entitled _Joco-Seriorum Naturæ et Artis Magiæ Naturales Centuriæ Tres_. It happened once in Mergentheim that there was a great fair, when the whole courtyard of the palace was full of earthenware vessels for sale _ab assidentibus muliebibus_ (by attendant women). Seeing this, the Prince of Mergentheim went about among these women, and so arranged it that they divided all their stock into two parts, or exact duplicates, half of which they hid away, while the other half was exposed for sale. While at dinner the Prince spoke much of magic, and professed to be able to produce such a delirium in people’s minds that they would act like lunatics. “Thus, for instance,” he said, pointing casually out of the window, “you see all those women. I can drive them mad at once.” Whereupon one who was present wagered a handsome carriage and four horses that the Prince could not do it. The latter smiled, waved his hand, and uttered a spell, when lo! all at once the market-women began, _bacchantium more_--like raging Bacchantæ--to attack their crockery with sticks and stools, and hurl it about, and dash it to pieces.

The one who had betted the chariot protested that it was a trick arranged beforehand. The Prince replied, “Well, the pots are all broken. If I can mend them again by a spell, wilt thou then believe?” The other said, “Most certainly.” Then the Prince waved his wand and said, “It is done. Let us go down into the courtyard and see.” And when there, sure enough they found the pots all whole again--at least they discovered others exactly like them in their places.

The legend continued that the Prince, though he kept the carriage and horses as a trophy, liberally paid for them. The author of the _Tres Centuriæ_, who does not record the secret of the little arrangement, declares that he does not know whether it was all done by a fraud or by magic. If it was the latter, I regret that the incantation by which broken crockery is mended is now lost. The most powerful spell known to me is _Recipe Gummæ Mastichæ duæ unciæ cum Spirito Vini fiat mixtio_--that is, mastic cement. It is generally combined with sturgeon’s bladder glue.

This cement answers very well for glass. One of the old recipes, which was very good indeed, is thus given by JOHANNES WALLBURGER (1760):--“Take finely cut and a little powdered sturgeon’s bladder” (still sold by all chemists), “soften it all night in spirits, add to this a little clean and powdered mastic, boil it a little in a brass pan. Should it become too thick, add a little spirits.” This may be also used for many other purposes.

A strong but coarser adhesive, especially for crockery and stone, can be made as follows:--Take old and hard goat’s milk cheese, and warm it in hot water till it forms, by pounding, a mass like turpentine. Add to this, while grinding, finely pulverised quicklime and the well-shaken white of eggs.

I do not hesitate to give a variety of such recipes, because in every one the artist will find valuable suggestions for other purposes than simply glueing broken articles together. This latter is a valuable “filler” for many purposes. Glue was formerly made into a strong cement by boiling it for a time in water, but before it had become incorporated with the water, the latter was poured off and strong spirits substituted and stirred well in.

A very popular old cement for crockery, of which there were several variations, was made by mixing glue, turpentine, ox-gall, the juice of garlic, and sturgeon-bladder, tragacanth, and mastic. All of this singularly smelling mixture was put into a pan and boiled in strong spirits, such as whisky, then kneaded on a board under a roller, again boiled with more spirits, yet again rolled, and this was repeated a third time, and then cooled till it could be cut into cakes. When these were to be used they were again steeped in spirits. But with this cement, glass or metal could be most firmly attached to wood. I confess that I have never tried it, but it was evidently a very strong cement.

Another of these somewhat complicated recipes for crockery, glass, and porcelain, which I find in the _Tausandkünstler_, 1782, is as follows:--Half an ounce of finely cut sturgeon’s bladder, two teaspoonfuls of alabaster powder or gypsum, quarter of an ounce of tragacanth, one teaspoonful of silberglatt, two of powdered mastic, two of frankincense, two of gum-arabic, one of Marienglas, one tablespoonful of spirits of wine, one of beer-vinegar. Boil it and stir, and apply. Any drops sticking to the mended article may be removed with vinegar. When it is to be used again revive it by heating, adding spirits of wine and beer-vinegar. The gum-frankincense is here worth noting.

A common cement for mending broken glass or china is prepared as follows:--To two parts of gum-shellac add one of turpentine; boil them over a slow fire, and form the mass into small cakes before it dries. To use it, warm with a lamp. To mend ivory or wood, take a cake and let it dissolve in spirits of wine.

A very strong cement is made as follows:--Take one ounce of finely powdered mastic dissolved in six of spirits of wine and two ounces of shredded sturgeon’s bladder dissolved in two ounces common spirits; add one half ounce of _gum-ammoniac_ as it hardens; warm it when it is to be used. This is as strong a cement as can be made.

Defects, cracks, and repairs in porcelain, &c., may often be concealed as follows:--Paint the spot with silicate of soda, not too much thinned, and dust it over before it dries with bronze powder. This will set so hard that it may be polished with an agate burnisher.

It is also possible that many of my readers have heard of _gesso painting_, an art perfected by Mr. WALTER CRANE. This consists of painting with plaster of Paris in solution, with the point of a brush, depositing the soft paste in relief. The same principle is applicable to painting in silicate and whiting on glass surfaces. By means of it decoration can be given to any glass bottle or other object.

LIME enters into the composition of many cements, the simplest being the mortar formed by its admixture with water. But the quality of this is very much determined by that of the lime. The _chunam_ of India, which resembles white marble or a fine white stone, is made of sea-shells burned to lime. A wonderfully hard, fine, white cement used by the Romans for their best mosaic-work, and which set with great rapidity, was made of shell-lime with the white of eggs. I have found the same composition worthless when made with inferior stone-lime.

A good cheap cement for porcelain and glass is combined as follows:--

Starch or wheat flour 8 Glue 4 Purified chalk 12 Turpentine 4 Spirits of wine 24 Water 24

Pour a part of the spirits and water mixed on the flour and chalk, add the glue, boil it down till the latter dissolves, and stir the turpentine into the whole. This can be used to make artificial wood with shavings or sawdust.

A very good cement for porcelain, and one which is colourless, is made by cutting the finest clear gelatine into bits, and dissolving it in vinegar of 50°, stirring it in a porcelain vessel until well mixed. When cold it will harden, but softens under the influence of heat, when it may be applied to the broken edges of the porcelain, which are to be pressed together. It will be perfectly hard within twenty-four hours. It is to be observed that the art of keeping such joined pieces together is the most difficult problem in mending. This cement is widely applicable to many objects, and also admits of considerable modification and additions, like all cements. As it is colourless, it may be combined with ivory dust, or white powders of baryta, magnesia, whiting, &c., to form artificial ivory with glycerine. With sturgeon’s bladder it makes a still stronger cement.

LEHNER observes that glue has the property, when combined with acid chrome salt (_sauren chromsalzen_), of losing its solubility when exposed to the light, so that it can be used as a cement for broken porcelain and glass. If the juncture is to be invisible, take the purest white gelatine; otherwise the cheaper gilder’s glue will answer. To prepare the chrome glue, dissolve the gelatine or the glue in boiling water, then add the solution of double chromic acid alkali, or the red chrome alkali of commerce, stir it well up, and put it into tin boxes.

The formula is:--

Gelatine or gilders’ glue 5-10 Water 90 Red chrome alkali 1-2 Dissolved in water 10

To use, warm the cement, apply it to the broken glass, which must then be exposed for several hours to the sunshine.

Cracked bottles are mended by a very ingenious process, described by LEHNER. The bottle is corked, but not tightly, and then exposed to heat about 100° centigrade. Then the cork is driven in tightly, which causes an expansion of the cracks, which are at once filled by means of a finely pointed brush with the silicate. Removed to a cooler place the glass contracts on the as yet fluid silicate, and the fractures are mended.

* * * * *

A VERY STRONG, CLEAN CEMENT FOR PORCELAIN OR GLASS is made as follows:--

Well-cleaned glass powder 10 ” fluor spar powder 20 Silicate of soda solution 60

This must be very quickly stirred and applied. This is one of the _hardest_ and best cements, and it resists heat and other influences so well that when very carefully amalgamated it may be applied to the manufacture of many useful articles. The same may be made with the substitution of white pipeclay for fluor spar, or with the addition of the same in somewhat larger proportion. Pipeclay or any good clay can also be combined with glycerine to prevent its drying. With gelatine and a _little_ glycerine it will harden and not crack.

This requires careful amalgamation and rapid work.

To prepare very fine glass-powder for this cement, heat any glass till red-hot, then drop it into cold water. It may then be reduced in a mortar to an impalpable powder.

Earthenware tubes or pipes which are to be exposed to intense heat may be luted or joined with the following cement:--

Peroxide of manganese 80 White oxide of zinc 100 Silicate of soda 20

“This does _not melt_, save at a very high temperature; and when melted it forms a glassy substance, which holds with extreme tenacity” (LEHNER).

To prepare _caseine_ cement for crockery or marble, it may be observed that we should always take _fresh_ white cheese and macerate or knead it thoroughly till only pure CASEINE remains. By adding to this one-third of powdered quicklime and blending the two ingredients very thoroughly we get a very strong glue. An admixture of 10 parts silicate of soda also forms a powerful cement.

The following for tile-work and common brick-crockery, or terra-cotta or porcelain, is very highly commended by LEHNER, who says that anything mended with it will sooner break in another place than where it is cemented:--

Slacked lime 10 Borax 10 Litharge 5

The cement is mixed with water, and the tile or crockery, &c., heated just before being mended.

I cannot insist too strongly on this--that no one is to expect that by simply taking recipes, as written, compounding and applying them, there will be a successful result at the first trial. We must always have the best material, often fresh, and generally attempt the application more than once. _Perseverando vinces_--“By perseverance you will conquer.” Not only must the _quality_ of the ingredients used be of the best, but the composition be made exactly in the order in which they are given. The same substances often give very different results, simply because the order of combination in the two was different.

TO REPAIR PAVEMENTS:--

Calcined lime 10 Purified chalk 100 Silicate of soda 25

This hardens slowly. It can, when mixed with small sharp-edged fragments of broken stone, be used to form pavements, or as a bed for mosaics. For the same purposes, or for cementing marble slabs, a cement known as that of BÖTTGER may be used. It is made thus:--

Purified chalk 100 Thick solution silicate of soda 25

This becomes (LEHNER) in a few hours so hard that it can be polished. It is the principal, and almost the only, cement used by M. RIS-PACQUOT, or commended in his work on mending crockery. It admits of a great variety of modifications. It is very superior as a bed for mosaics of all kinds. It forms, like the preceding, also a good bed for scagliola and ceresa.[1] I would here say of the latter, that I could wish to see it more generally used for mural or wall ornament, since any one who can paint a face or decoration boldly and largely in oil or water colours will find it very easy. It admits of rapid execution, and is striking from its brilliancy. Everything in it depends on having a good bed to which it can easily adhere. I may here observe that beds like these which set hard and _fine_ are also adapted to fresco-painting, in which the difficulty is to select colours which, when absorbed and dried, do not fade. Most paints made from mineral substances combine with silicate of soda.

I may here remark that a curious and easy art, very little known, consists of carving or cutting low reliefs on tiles or terra-cotta or brick-like ware, which, when outlined or in relief, can be glazed in colour with silicate of soda; also with many other cements.

A common and good CEMENT FOR PORCELAIN OR GLASS is made as follows:--

Calcined gypsum or plaster of Paris 50 Calcined lime 10 White of egg 20

This must be quickly mingled and rapidly used, as it sets very rapidly and becomes extremely hard. It makes an admirable bed for mosaics or ceresa.