Part 4

When plaster of Paris is simply combined with burnt alum in water, the objects mended with it require several weeks to set or adhere. Gypsum combined with gum alone holds firmly, but does not resist water (vide _General Recipes_).

CEMENTS FOR LUTING or closing chemical apparatus:--

Dried clay 10 Linseed-oil 1

This endures heat to boiling-point of quicksilver.

A more resistant fireproof is as follows:--

Manganese 10 Grey oxide of zinc 20 Clay 40 Linseed-oil varnish 7

Of the oil only so much is needed as to combine the mass to a paste.

A LUTING for very high temperatures:--

Clay 100 Glass powder 2

Another CEMENT:--

Clay 100 Chalk 2 Boracic acid 3

LEHNER has in his work on Cements many valuable suggestions as to mending porcelain. _Firstly_, that in such mending, the adhesive be applied with care, in as even and as thin a coat as possible; to which I would add, that the unskilful amateur is apt to daub it on irregularly and carelessly, with the impression that the more cement there is the better it will stick, which is just so far wrong that every superfluous grain is just so much of an impediment to good drying or adhesion. Again, the inexpert daubs it on with a stick or “anything,” when a fine-pointed brush or hair-pencil should be used.

BROKEN CHINA WHICH IS TO BE MENDED should be carefully covered away so as to protect it from dust, which is hard to clean off. Beware of fitting the pieces together again and again, as is often done.

If the broken china was used to contain milk or soup, &c., it should be laid in lye to dissolve all the fatty substance, and then be washed with clear water. Painted porcelain cannot, however, be laid in lye, which would ruin all the colours; in this case wipe them clean with dilute acid.

The great difficulty in mending is to bring the pieces together and keep them so till the adhesive dries. LEHNER recommends that when objects are small and costly, a mould of gypsum be constructed round them. In most cases putty or wax is far more manageable. As before remarked, indiarubber bands are chiefly to be relied on; even if not capable of holding permanently, they aid greatly in tying with cord.

In the Manual of F. GOUPIL, rewritten by FREDERICK DILLAYE, the following method of restoring broken vases, &c., is commended:--

“Form a solid mass of clay in the form of the original object. Then place on it, one by one, the fragments in their place, keeping the clay moist. When this is done, paste over the exterior strips of paper, in sufficient quantity to hold the whole firmly together. Then remove the moist clay, and paste strong slips of paper” (or thin parchment) “over the interior so as to hold the whole. Then” (when dry) “carefully moisten and remove the outer coating.”

The author mentions that this is only applicable to vases the mouth of which is wide enough to permit the hand to be introduced. I would here, however, add, that even when it is too small for this purpose, the restoration can be equally well effected as follows:--Make the core of wet clay, or, better, of beeswax, then paste over it thin tough paper. Cover this with gum-arabic solution, and set the pieces on it. When dry, melt out the wax or clay.

Fish-gum, _colle de poisson_--that is to say, what is generally called _sturgeon’s bladder_, which includes the bladder of several kinds of fishes dissolved--is best for glass, marble, porcelain, and all kinds of mending where the cement should not show. This, when combined with oil, is _said_, if mixed with cloth-dust and fibre of wool or silk or cotton, to spin up into thread.

MENDING GLASS

WITH SEVERAL ALLIED PROCESSES

APPROVED CEMENTS--SILICATE OF SODA

“_Glück und Glas Wie bald bricht dass._”

“_Good luck, like glass, Soon breaks, alas! Yet skill can bring it so to pass As to mend a fortune or a glass._”

--Old German Proverb.

Putty is naturally the first cement which suggests itself in connection with the mending of glass, since this latter material is most familiar to the world in the form of windows, although in many places--as, for instance, Florence, where it is called _mastico_ and _pasta_--it is little used or known. The word is from the French _potée_, which also means a potful. It is very useful, not only for setting glass-panes, but for filling holes in wood, and forms a part of certain mixtures as a cement for moulding ornaments. It may be weak and brittle, or else strong and very hard, according to the manner in which it is prepared. It is commonly made by combining chalk in paste, with water, with linseed-oil; other powders are also used. In America it is made with pulverised soap-stone and oil. Its excellence depends on the quality of the oil and the care with which it is kneaded. It should be kept in a damp cellar, in wet cloth or under water. Should it dry and become brittle, fresh oil must be added.

“_To take hard old putty from glass window-panes_, cover it with a mixture of one part of calcined lime, two of soda, and two of water” (LEHNER). Oxide of lead combined with oil makes an excellent but yellow putty. It sets very hard.

The white or grey oxide of zinc combined with linseed-oil or linseed-oil varnish makes a cement which is used for making glass adhere to wood or metal.

_Thick lacquers_, such as copal or amber, may be used instead of common varnish with better effect, and the composition is better when calcined lime or oxide of lead are added. The excellence of the cement depends on the degree to which the ingredients are amalgamated or rubbed in together; and this rule holds good for all similar mixtures.

_Varnish_, or heavy or “flat” lacquer of copal or amber, forms of itself a strong adhesive, with the only drawback that it takes a long time to dry.

A VERY GOOD CEMENT FOR GLASS (LEHNER) is as follows:

Gutta-percha 100 Black pitch (asphalt) 100 Oil of turpentine 15

This is a glue of general application, and specially good for leather and mending shoes.

The reader who would thoroughly study the subject of glass may consult _Die Glas-Fabrikation_, a very admirable work by Raimund Gerner, glass manufacturer; A. Hartleben, Vienna and Leipzig, price 4s. 6d.

Small triangles of sheet tin or iron are often used to fasten panes.

The mending of broken glass is in most cases much the same as that of broken crockery or porcelain. The cement made from mastic, or mastic combined with sturgeon’s bladder, or generally of silicate with whiting, is the proper adhesive. As silicate of soda is simply liquid glass, it can be employed to fill spaces or to make glass; but, owing to its sticky nature, it is hard to manage. This may be often effected by first preparing a layer of soft paper, on which successive coats of silicate are laid. When dry the paper can be washed away.

SILICATE OF SODA has become of such importance that a French work on mending fictile ware is almost entirely limited to its use as a binder, when combined with whiting. _Water-glass_ was long supposed to be a modern invention, till some one found it described in Van Helmont’s works, A.D. 1610. But I have found it also in the _Joco-seriorum Naturæ_, 1545; in the _Magia Naturalis_ of Wolfgang Hildebrand, which is of the same time; and, finally, by _Paracelsus_ (_Liber de Præparationibus_), where he describes it as _Destillatio Crystalli_. And the author of the _Joco-seriorum_ speaks of soft glass as a thing which had been treated by several writers.

According to WAGNER there are three kinds of soluble glass--(i.) the soluble potash glass, 45 silex, 3 charcoal, 34 carb. potass.; (ii.) soluble soda glass, 100 pts. quartz, 60 cal. sulp. soda, 15 of charcoal; (iii.) double soluble glass, 100 quartz, 22 cal. soda, 28 carb. potass., 6 wood-coal. Water-glass combines well with any “indifferent” powder, such as powdered glass, to make a strong cement. To powder glass, heat it red-hot, drop it into cold water and pulverise it. It will become as fine as flour, and in this state combines with gum-arabic, or glue, or gums to make a powerful glass-mender. Mixed with powdered glass, oxide of zinc, or whiting, powdered marble, calcined bone, plaster of Paris, wood-ashes, &c., it can be worked like putty. Mixed with colours it is used for stereochrome painting, a kind of fresco.

Missing pieces of glass, such as leaves from a chandelier, can be easily replaced with water-glass, and all cracks or defects glazed over with it.

This mending is allied, however, to certain processes in art which are so interesting that I venture on a description of them.

A great deal of mending and restoring in glass can be effected by means of the blow-pipe and spirit-lamp or gas-flame. Difficult as this may sound, it is not only an easy, but also a very curious and entertaining, occupation. In any city an expert or workman may be found who would give a few lessons. I have very often been impressed with the fact that so little artistic invention or originality is found in glass-work. Even the far-famed Venetian work is extremely limited, and “mannered” or conventional, compared to what it might be.

The following is an old recipe for repairing glass:--Take finest powdered glass, best mastic, with equal parts of white resin and distilled turpentine. Melt all well together. To use, gradually warm it and then apply.

Quicklime and white of egg, intimately rubbed into one another on a flat surface, make a good cement for ordinary glass or pottery.

The cement of _gum-arabic_ is much stronger when made as follows:--Take gum-arabic and dissolve it in acetic acid (vinegar) instead of water. It must be melted in a hottish place, as it will in that case be much better. The finest quality of sheet-gelatine makes a transparent glue, invaluable where colour is to be avoided.

TO MEND A CRACKED GLASS BOTTLE OR DECANTER.--Heat the bottle, pressing in the cork, till the hot air within expands the cracks, which must be at once filled with the liquid glass. Then, as the water-glass is driven in by the pressure of the outer air, as the bottle cools the cracks are closed.

You cannot well mend a broken looking-glass, but something can be done with the large pieces. Varnish or paste a piece of paper and lay it on the quicksilver. Then with an American glass-cutter, price one shilling, or a diamond-cutter, divide them into squares for small mirrors. Two of these of equal size can easily be converted into a folding kaleidoscope (not described by BREWSTER in his work on the Kaleidoscope). Lay the two pieces face to face, and paste over the whole, on the quicksilvered side, a piece of thin leather or muslin. When dry, with a penknife, cut a slit down between the two on three sides. It will then open and shut like a portfolio. This may serve as a travelling, looking or shaving glass, but it is very useful to designers of patterns. Place the glass upright on a table at a right angle, or more or less, and lay between the mirrors any object or a pattern, and you will see it multiplied from three to twelve times, according to the angle. Beautiful variations of designs can thus be made, _ad infinitum_. They may be used as reflectors, when placed behind a light.

Take such a piece of looking-glass and lay a piece of paper on the back, and then with an agate or ivory point write or draw on it, but not as hard as to break the silvering. Then turn it to the sun or a strong light, and let the reflection fall on a white surface. Though nothing be perceptible on the face of the mirror, the writing will appear in the reflection.

Glass is engraved as metal is etched; with this exception, that, instead of sulphuric or nitric acids, fluoric acid is used. Both glass and _china_ can also be directly etched with a steel point, aided by emery powder; which latter art I have never seen described, but which I have successfully practised. It is fully set forth in my forthcoming work on “One Hundred Arts.”

Malleable glass, or at least that which does not break easily when let fall, is prepared by dipping the objects made from it, while quite hot, into oil. I conjecture that panes of window-glass thus prepared would not be broken by hail, as I have observed that plate-glass is not.

It sometimes happens that goblets of thin glass--especially those which have had a peculiar kind of annealing or tempering--ring beautifully when blown on so as to vibrate them. The effect is almost magical on one who hears it for the first time. I mention it that the reader may, when he finds old Venetian or any other thin glass goblets for sale, see if there be not among them a finely ringing one. An organ could be thus made to play by wind. With regard to music on glass, take any ordinary bottle, and by rubbing on it a cork a little wetted you can, with a little practice, produce a startling imitation of the chirping, and even warbling, of birds. I knew one who could thus imitate to perfection nightingales and call forth responsive songs. The effect depends in a degree on the quality of the cork, and also that of the glass. With a violin-bow very musical sounds may be drawn from the edge of a pane of glass. It seems as if these methods might also be developed into musical instruments. It is well known that tubes of glass suspended when a candle is placed beneath them give forth musical sounds, often of great richness and strength. There are also the musical glasses, which may be played in two ways, either by rubbing the edges with a wetted finger or by filling the glasses more or less with water till an octave is formed, and then tapping them with a stick of wood. All of which has, indeed, nothing to do with mending glass, yet which may not be without interest to those who wish to learn all its qualities.

Among GLASS CEMENTS in common use which can be recommended are the well-known Polytechnic, also the Imperial Liquid Glue (no heating required), Hayden & Co., Warwick Square, London. There is also a very good glass cement made and sold by Keye, filter-maker, Hill Street, Birmingham.

The Venetians made ordinary glass goblets very beautiful by painting on them in relief with a substance which I suspect was in some cases a form of silicate, or else with a kind of paint which was not enamel, yet which seems to have been partly vitreous. It rather resembles oil paint with glass powder, but I doubt if it was this.

Working in glass implies the mending and restoration of stained-glass windows; that is, of painting on glass and a study of designs. Of all this there is almost a literature. Among other works I can commend _A Book of Ornamental Glazing Quarries_, by A. W. Franks, £1, 1s.; _Divers Works of Early Masters in Ecclesiastical Decoration_, by Owen Jones, £3, 10s.; _Westlake’s History of Stained Glass_, vol. i., _Fourteenth Century_, 13s. 6d.; vol. iii., _Fifteenth Century_, 18s., published by Batsford, 52 High Holborn. At Rimmel’s, in Oxford Street, the reader can generally obtain these, and all works on similar subjects at prices much below the original cost.

A MENDING CEMENT FOR GLASS is made as follows:--

Common cheese 100 Water 50 Slacked lime 20

This is found in many books of recipes. It must be observed that the cheese is to be for sometime carefully pounded with the water till quite soft, and the lime then very quickly stirred in. This is not only useful to mend glass, but can be applied to many other purposes. The cheese is best when fresh.

CASEINE (or pure cheese) can be combined with ease with liquid silicate of soda (LEHNER), and thus forms a very strong cement for porcelain or glass, or any other material. Fill a flask with one-fourth of fresh caseine to three-fourths of silicate, and shake it thoroughly and frequently.

Another formula is as follows:--

Caseine 10 Silicate of soda 60

This must be used very promptly, and the article mended dried in the air.

A CEMENT which may be used in several combinations is made by dissolving fresh acidulated caseine (made by adding vinegar to milk, and carefully washing the deposit) in a very little caustic lye. It must be kept corked in bottles.

These _caseine_ or cheese or curd cements hold well, but do not well resist water, except in powerful combination.

The excellence of cements depends to a great degree on the quality of the materials and the scrupulous observance of care in making. Thus for the following, for glass:--

Glue 200 Water 100 Calcined lime 50

in which we have one of the commonest and oldest formulas, the value depends on “the make-up” that is, the glue must be left in cold water for two days, then boiled in a _balneum mariæ_, or a double kettle, in lukewarm water; that is, it must not boil, or the glue will be weakened.

The so-called DIAMOND or TURKISH CEMENT, for glass or any other fine work, has been known since early times as incredibly strong. Its formula, according to Lehner, is as follows:--

I. Sturgeon’s bladder 20 Water 140 Spirits of wine 60

II. Gum-mastic 10 Alcohol 80

III. Gum-ammoniac 6

These are three separate portions, No. I. being prepared by warming and filtering. The gum-ammoniac is reserved from the others, and added _after_ they are mingled.

A STRONG BASE FOR A CEMENT FOR GLASS, as well as wood or stone, is made by gradually stirring finely sifted wood-ashes into silicate of soda, or strong acid glue, till a syrup-like substance results. In America the best ashes for this purpose are those of the hickory. Perhaps beech wood yields them equally good.

There is a DIAMOND CEMENT which is of special value to attach gems to rings or metal, to make coral or pearl or ivory adhere together, and, in short, for all fine work where a very strong adhesive is required. It is as follows:--

Sturgeon’s bladder 8 Gum-ammoniac 1 Galbanum 1 Spirits of wine 4

The sturgeon’s bladder is cut into small pieces and steeped in the spirits, and the rest, in solution, then added. It must be warmed again when used.

As this cement will bear long exposure to moisture before being at all injured by it, it can be used as a medium for painting on glass, and thereby producing effects very little inferior, either as regards beauty or durability, to glass itself. The experiment can be easily tried, as any chemist can make up the recipe. When finished, the painting can be coated with liquid silicate of soda, which will give it all the property of glass.

A LIME CEMENT FOR GLASS is made as follows:--

Calcined lime 30 Litharge 30 Linseed-oil varnish 5

JEWELLERS’ CEMENT. Extremely strong:--

Fish-glue solution 100 Mastic varnish (pure) 50

The fish-glue must first be dissolved in spirits of wine.

TO JOIN GLASS AND METAL, &c.--Stir slacked and powdered lime in hot glue. This sets as a very hard substance. It can be extensively modified and varied for many substances, and used for painting.

CEMENT FOR GLASS:--

Gum-arabic 50 Sugar 10 Water 50 Oil of turpentine 10

The gum, sugar, and water are first carefully combined, and then the turpentine well stirred with the mixture.

SALLE’S CEMENT FOR GLASS:--

Muriate of lime 2 Gum-arabic 20 Water 25

Not commended by LEHNER, as being too soluble. TO CLOSE BOTTLES:--

Powdered resin 6 Caustic soda 2 Water 10

To be thoroughly mixed and left for several hours. Before using, stir well into it eight to nine parts of calcined plaster of Paris. This will in half-an-hour take firm hold or “set,” and is waterproof. A good filler for cracks.

The reader who desires to be perfectly informed as to glass in all its relations can obtain, by application to J. BAER, Rossmarkt, Frankfort on the Main, Germany, a catalogue which is perhaps the most extensive on the subject ever published.

Coloured or stained glass windows may be repaired or made by the following process, which has the advantage of being quite as durable as any in which the colours are burned in:--Take two panes of glass, and paint on one your pattern with fine varnish and transparent colour mixed. When dry, go over the whole, with a broad, soft brush, with a liquid mastic cement, which must be quite transparent and thin. Any transparent strong cement will serve, but it is advisable to use the mastic in all cases as a narrow border and at the edges. If you have an engraving, especially one on very soft spongy paper, take a pane of glass, cover it with a coat of varnish, and just before it dries press the engraving face down, on it. When quite dry, with a sponge slightly damped and the end of the finger, peel away all the soft paper, leaving the lines of the engraving. These may now be coloured over, with even very little skill and care. A very good effect may be produced, so that a very indifferent artist can in this way produce very tolerable pictures. Then, to better preserve this, double it with the other pane.

By painting and shading also on this _second_ pane, as I have discovered, very beautiful and striking effects of light and shade can be developed, so that this forms, as it were, a new art by itself. This will remind the reader of the porcelain lamp-shades, which so much resemble pictures in Indian ink; but the effects of the double panes are more singular and far more varied. There may be even a third pane employed. As the materials for this art are far from expensive, and as it is extremely easy, I have no doubt that it will be extensively practised. Protecting one glass picture by another is not a new art; but I am not aware that the obtaining a series of lights by thus reduplicating the panes has been practised.

A modification of it is as follows:--Cut out several panes, corresponding to the size of the two glass covers, of quite transparent paper or parchment, prepared by rubbing with oil or vaseline, lard, or the like. Paint on these the required modifications of the picture. The advantage of this is, that a great many shades can thus be given in a thinner space, creating an astonishing effect. As this is not at all a mere imitation of stained glass, and as it produces effects not to be found in the latter, it may rank as an art by itself. The chief of these effects is _relief_, especially shown in the human figure. But the most extraordinary are the variations of chiaroscuro which it affords, by availing himself of which the artist may create or obtain striking suggestions for oil or _aquarelle_ pictures; for these transparencies can be so infinitely and ingeniously varied that no one can fail to derive from them many ideas.

This may be tested by simply preparing any picture, say of a statue, a castle on a rock, or a face. Cut out from sheets of the same size in very transparent paper a series of shadows adapted to it, and adjust them. They may be all in monochrome or one colour, or in many hues. They may range, with proper care, from almost imperceptible shadow to opaque black. By beginning with only two stencils or shaded pictures--for as regards these the artist must be guided by his own skill--and gradually increasing the number, the proper adjustment will soon be found. I advise the beginner in copying to proceed from monochrome to two colours before attempting many. Teachers in _aquarelle_ will find that such copies are--after a certain degree of proficiency shall have been obtained--much superior to those commonly used, as they come nearer to nature.