The history of modern glass begins, as I have said, with the famous Venetian cristallo of the sixteenth century. Many other varieties were made at this time, but it was the absolutely colourless and transparent glass, capable of being blown to extreme thinness and then worked into every variety of form, that above all established the European reputation of the Murano glass-workers. Before long, in nearly every country of Western Europe, the old methods of working were falling into disuse; and by the aid of skilled workmen who were tempted away from Murano, or, failing that, were hired from the rival glass furnaces of L’Altare, the attempt was made to imitate this clear white glass of Venice.

We have, then, in this cristallo the typical glass of Venice, and here more than in any other group, whether of earlier or of later date, we find a family of glass of which the artistic merit depends directly upon the skill of the glass-blower, rather than on that of the enameller or engraver. In the simpler and earlier specimens, an undeniable charm is derived from the extreme tenuity of the material—there is an evanescent and almost ghostly air about the ‘diaphanous, pellucid, dainty body’^[147] of not a few of these glasses. Although entirely free from any positive colour, there is often a certain tendency to greyness in the metal, and this is increased to a misty cloudiness when the surface has been attacked by atmospheric influence, as is not unfrequently the case with glasses that have been long exposed to our damp English climate.

There is little change or development to be observed in the glass of this character made at Murano during the sixteenth and seventeenth centuries, nor is it always safe to regard contorted shapes and elaborate decorations as necessarily a sign of a late origin. This caution is confirmed by an often quoted passage from Sabellico, the learned librarian of St. Mark’s and historian of Venice; it is from a Latin work, De Situ VenetÆ Urbis, written about 1495. We can form from it some idea of the wonderful variety of the outturn from the Murano glass-works at that time, and of the elaborate shapes that were already given to the vessels. When we pass, says Sabellico, from Venice to the suburb of Murano, we are struck by the grandeur and size of the buildings; it appears from afar as a city, extending for a mile in length. The island owes its chief renown to its glass-works. It was a famous discovery to make glass that should vie with crystal in clearness. Since then the nimble wit of the workmen and the never-resting care to find something new have led them to apply to the material a thousand various colours and shapes without number. Hence the calices, the flasks, the canthari, the ewers, the candelabra, the animals of every race, the horns, the beads (segmenta), the bracelets, etc. etc. So far Sabellico—the good man is, I am afraid, more concerned with his latinity than with the matter in hand: but this is a weakness that he shares with more than one writer of this time. He goes on to speak of the ‘Murrhine vases’ made at Murano, of which the only fault is their cheapness; all these marvels had the Venetian galleys brought before the eyes of the nations, so that, wondrous to say, by familiarity they had become as things base and common.

In the means adopted by the Venetians to adorn their cristallo we are at times taken back to Roman methods. The handles, often of blue glass, and the stringings and frillings that surround the body are applied hastily but skilfully by the light hand of the workman. This kind of ornament reached its completest development in the tall beakers and vases with handles that took the form of wing-like excrescences. These ‘winged beakers’ were afterwards copied and the forms exaggerated in Germany and in the Netherlands, where they were held to be especially characteristic of the now fashionable glass of Venice.

It is certainly remarkable how little this Muranese glass as a whole reflects the glorious Venetian art of the cinquecento. Apart from some of the earlier enamelled and gilt examples and from the simpler forms of the pure thin cristallo, we can find among it little that is quite satisfactory from an artistic point of view. Much even of the sixteenth-century glass is merely fantastic, and appeals only to childish tastes. The bulk of it was probably made for foreign markets, for the dull northern barbarian, whose attention had to be caught by something new and extravagant.

Little heed is paid to this more elaborately decorated glass by the great contemporary painters. In fact, I can find no example of it in their works. When glass is introduced, it is invariably of the simplest description. In the big altar-pieces of Giovanni Bellini, of Cima, or of Carpaccio, the glass lamps that hang from the roof are in the form of little conical cups of plain outline. Amid all the elaborate staffage of Crivelli’s pictures, the lily on the table or ledge beside the Virgin stands in a little cylindrical beaker of glass, for all the world like a modern tumbler.^[148] So in the next century we may search in vain in the pictures of Titian or of Veronese for elaborate examples of Venetian glass. In the banquet scenes of the latter painter, the wine indeed is served from graceful decanters with tall necks and globular bodies, and is drunk from tazza-shaped goblets of glass,^[149] but on the credenza or buffet at the side, the gold and silver plate is never relieved by examples of our material.

A curious account of a banquet given at Mantua, on the occasion of the marriage of the Marquis, is quoted by Mr. Nesbitt from a contemporary writer. There was, we are told, on this occasion such a display of ‘diversi bicchieri, carrafe, e giarre ed altri bellissimi vasi di cristallo di Venezia, che credo vi fussero concorse tutte le botteghe di Morano!’ And there was need of this store, he adds, seeing that after they had drunk, the guests proceeded to break the glasses they held in their hands ‘per segno di grande allegrezza.’^[150] We are reminded of the feast described by Joinville, though in that case the glasses were swept off the table by the well-aimed Bible of one of the guests (see p. 136).

I shall now have to pass in rapid review the principal varieties and applications of the glass made at Murano in the sixteenth and seventeenth centuries.

The Frosted or Crackle Glass is perhaps the simplest modification of the pure cristallo. To produce this, the paraison is plunged rapidly into cold water, and after reheating to the necessary degree, but not beyond, it is worked into the desired form. A similar effect is at times produced by rolling the molten paraison upon fragments of crushed glass. I have spoken in the introductory chapter of certain rare cases where a minute fissuring has been set up in the substance of the glass. This true crackle is probably in all cases the result of a subsequent structural change.

Latticinio, Lattisuol, or Lattimo are names given by the Venetians to a milk-white opaque glass. White enamels were freely used in the fifteenth century, but the earliest known specimen of Venetian glass, the whole body of which is rendered opaque by the presence of oxide of tin (calcina di stagno)—the vetro bianco di smalto of the early writers^[151]—can hardly be older than the beginning of the next century.

The spherical vase (Slade, 402) formerly in the possession of the Marquis D’Azeglio, is an exceptionally beautiful example of this milk-white glass (Plate XXXII.). The gilt scrolls harmonise well with the slightly warmish ground, and were it not for the rudely executed mermaids on either side, an Eastern origin might well have been sought for this quite exceptional piece; in fact, I do not know of any other specimen of undoubted Venetian glass so distinctly Persian in character.

In the Museo Civico at Venice is a flask (circa 1530) of this lattimo glass, about five inches in height, decorated in blue, with allegorical subjects. Although somewhat rudely executed, the painting is masterly in style, and may be compared to that on the best contemporary majolica (Plate XXXIII.). At a first glance this little vase might be taken for an example of Medici porcelain, and indeed we must bear in mind that all through the sixteenth century attempts were being made in Venice to imitate the porcelain of the Far East, more especially the plain white and the blue and white wares which were already arriving at Venice in considerable quantity.

This lattimo glass came much into favour for a second time early in the eighteenth century; it was at that time often decorated in colours in a pseudo-Japanese style. This later milk-white glass is once more closely associated with the attempts then again made at Venice, as in so many other countries, to imitate the porcelain of China and Japan. This had indeed, before the end of the previous century, been in a measure accomplished in France by means of a soft paste, in the composition of which a glass-like frit played an important part. At a still later time this lattimo glass was even painted in monochrome, in imitation of our early printed Worcester porcelain!

Closely based upon this latticinio—for the threads in a vast majority of cases are of an opaque white—is the famous Vetro di Trina or lace-glass. At the beginning of the last century the art of making this net-work decoration appears to have almost died out, but in the thirties and forties it was revived by Domenico Bussolin, and when later on more interest began to be taken in the Murano glass, it was to this vetro a reticelli that at first most attention was given. The details of the manufacture were described and illustrated by the well-known director of the Choisy glass-works, M. Bontemps (ExposÉ des moyens employÉs pour la fabrication des verres filigranes, 1845).

There is, however, a simpler and perhaps easier application of these bands of lattimo, in which they are applied in a series of festoons to the surface. In this case the opaque white enamel appears to have been laid on to the paraison at an early stage and dragged into crescent-shaped waves, so as to resemble closely the decoration of the little flasks of coloured glass from Egyptian and early Greek tombs—to those later examples more especially, from Rhodes and Cyprus, on which the colours are only applied to the surface (p. 37), the resemblance in technique is very close. There are many interesting specimens of this festooned latticinio in the British Museum. In the case of the little biberon (Slade, No. 628) the festoons are worked into a palm pattern, identical with that often found on the little primitive vases.

I shall not attempt to follow in detail the manner of preparation of the true vetro di trina,—suffice to say that it is built up of a number of juxtaposed rods; these rods are arranged perpendicularly, side by side, so as to form a hollow cylinder, and into the midst a small vesicle of molten glass is inserted; to this the rods adhere, and the whole mass is then worked into the desired form. The rods themselves—they are similar to the canne supplied to the suppialume workers (p. 187)—may be either of opaque or clear glass, or they may be formed of elaborate combinations of the two (canelle a ritorto o merlate); the most complicated patterns are thus obtained. When two series of these rods are arranged to cross one another at an angle, we get a reticulated pattern, and within the reticelli thus formed a bubble of air may be caught up. There is, indeed, little opportunity for finding in this kind of work any free play for the decorative feeling of the artist, and the result of all these ingenious combinations of crossings and interlacings is only too often to give a tame and machine-made air to the finished vase or tazza.

The Opalised Glass, the Calcedonio^[152] of the Venetians, is obtained by adding the same materials as in the case of the latticinio, but in very small proportions: it stands to the latter as weak milk and water to pure milk. In practice, I believe, the opalescence is often given by the addition of phosphate of lime in the form of bone-ash, sometimes, perhaps, by arsenious acid.^[153] Pale blue by reflected light, it takes various orange and yellow tints when the light is transmitted through it. Such a vessel as the cylindrical goblet and cover of thick calcedonio in the Waddesdon Room at the British Museum, with a design in high relief representing the Triumph of Neptune, must have been cast in a mould.

We now come to certain varieties of glass which were much admired at one time, but are now little in favour. The aim, it would seem, in this class, as in the case of the old Roman prototype, was to imitate various kinds of precious stones and marbles. But the Venetians showed here little of the restraint of their classical predecessors, so that on the whole the colours, where not crude, are huddled together in muddy compounds.

An opaque red glass resembling jasper was probably known at Murano as early as the fourteenth century. In an inventory of the property of the Duke of Anjou (circa 1360) there is mention of a ‘pichier de voirre vermeil semblable a Jaspe.’ So in the next century, Charles the Bold possessed ‘Ung hanap de Jaspe garni d’or, À oeuvre de Venise’—to judge from the expression used this beaker was also of glass.^[154]

Already in a Milanese manuscript of 1443 (described below) there is a formula given for making schmelz by means of a mixture of certain salts of silver, iron, and copper, and before the end of the century we have Sabellico’s complaint that the modern murrhine glass was becoming far too common (see page 201); so that, on the whole, this family of marbled glass is, perhaps, as old as any other Venetian glass of which we have specimens. The examples, however, that have survived appear to be mostly of a somewhat later date. We find imitations of both classes of the Roman millefiori—the tints, however, are generally crudely matched—and especially several varieties of marbled glass with contorted veins of many colours. The schmelz par excellence of the Venetians (the German name would seem to point to a northern origin) is an irregularly veined and mottled mass, a somewhat unpleasant combination of bluish-green and purple tints, calling to mind certain kinds of slag—indeed it may have originally been made in imitation of some such substance. There are a few exceptionally fine early examples of this schmelz at South Kensington. Notice above all the spherical vase from the Castellani collection with cinquecento mountings and serpent handles of copper gilt; the greenish-yellow and pale blue tints are in this case harmoniously blended. To judge from the form of the bowl and stem, the cup of finely marbled schmelz at Hertford House cannot be dated much later than 1500. In this case, and probably in others also, the marblings are only on the surface; the interior is of a uniform greyish-green colour.

Of scarcely less importance is the splashed ware for which we can again find a Roman if not an Egyptian prototype. The splashes of enamel of various colours must have been scattered over the paraison at an early stage, for they have had to follow the changes of form given to the surface in the shaping of the vessel: we see them stretched out at the neck on the little burette in the Slade collection (No. 783). This splashed glass was much admired by the French and successfully imitated by them.

Something should be said of the painted Venetian glass of the seventeenth and eighteenth centuries. I say ‘painted,’ for such it is in general effect, although the pigments have probably in most cases been subjected to some kind of firing. The very poverty and dulness of the colours are indeed a proof of this; the artist’s palette has been subjected to the exigencies of the enameller’s muffle. We find landscapes with classical figures and amorini painted on the lower surface of bowls and rondelles (tondi). In the Dutuit collection, now housed in the Petit Palais at Paris, is a circular dish some fifteen inches in diameter, painted on the under surface, so as to be viewed through the glass; the subject, a dance of cupids, is treated in an exceptionally fine style and can scarcely be later than the middle of the sixteenth century. In many cases these designs have been added to Venetian glass by non-Venetian, sometimes by northern hands. This kind of painting or enamelling is, however, very subject to injury by use, and doubtless for this reason it is sometimes protected by a second sheet of glass. We have in such painted dishes a variety of the so-called verre ÉglomisÉ to which reference has already more than once been made.

The Venetians at times drew designs on their glass with a diamond. There are some examples of this in a good cinquecento style in the Slade collection; but this work was confined to the pure scratched line, and even shading was not much used. It was not till the eighteenth century that they began to copy the later German methods of deep engraving and cutting with the wheel.

The British Museum has lately acquired a square plaque of clear thick glass; at the back, in deep intaglio, is the portrait of a Doge, who, on the ground of the letters A. G. on either side of the head, may be identified with Andrea Gritti (1523-1538).^[155] The late M. Piot has extracted from a fifteenth-century treatise on architecture by Antonio Averlini a dialogue between two artists upon some curious applications of glass. We hear of cristallino plaques with figures carved on the lower surface, so as apparently to stand out in relief—a description which would apply well enough to this piastra.

There is no more troubled story in the history of glass-making than that of the manufacture of Mirrors at Murano from the fourteenth to the eighteenth century. We have seen in the early days, when these mirrors were backed with lead (p. 138), that the Germans had already become experts in this department. More than once in the Venetian archives there are references to the secret methods of these Todeschi. In a petition of 1503 there is mention of a plan for making good and perfect mirrors, a precious secret unknown except to certain Germans. It is impossible to resist the suspicion that there is here a reference to the cylinder process, which, as we have seen, was already known to Theophilus (p. 129); by this process it would have been possible to produce a fairly large and comparatively flat sheet of glass. The Venetians, on the other hand, probably continued to a late period to use the old method of ‘spinning’ or ‘flashing.’^[156]

It was only after the middle of the sixteenth century that the mirror-makers, the specchiai, formed themselves into a separate corporation; but in this guild were included, it would seem, the makers of the so-called mirrors of steel.^[157] Thus we find that in 1574, one Francesco Zamberlan, who only two years before had taken out a patent for his ‘specchi d’acciaio,’ was admitted to the new guild on the ground of his special knowledge. Those engaged in the polishing—the lustratura and spianatura—of both materials, glass and metal, were also members of the guild.

For us the interest in these mirrors lies rather in the framing. We find the new corporation early engaged in quarrels with the painters and with the workers in tarsia, mother-of-pearl, and coral (i miniatori, i marangoni, e muschieri), who found employment in decorating the frames.

For a time, no doubt, the Venetian mirrors held their own, but before the end of the seventeenth century the French, thanks to the energy of Colbert, had not only learned all their secrets, but by an entirely new method—namely by a process of casting or founding, and subsequent rolling and polishing of the glass plates—were able to meet the demand for the large mirrors that were now regarded as indispensable in a Louis-Quatorze salon. But these ‘glaces de St. Gobain’ are of an entirely different nature from the exquisitely framed little lustri with which we are now concerned. Unfortunately, as far as I know, there are no characteristic specimens of these cinquecento mirrors—at least of those in which glass forms an important element in the frame as well—in any of our public collections. For fine examples of such work we must go to the Louvre or the HÔtel de Cluny. It will be noticed that the margin of the glass is invariably bevelled, thus forming a transition to the elaborate framing. These cinquecento Italian mirrors were extensively copied, and this at an early date, both in France and at Nuremberg.

In spite of the heroic efforts made by the authorities in the late seventeenth and in the following century to introduce the new methods of working glass at Murano, the Venetians failed to maintain their position. It was only in the more conservative Eastern markets that the demand for their mirrors was kept up; even to-day, in Syria or in Persia, these Italian glasses may not unfrequently be seen in private houses and even in mosques.

Another characteristic application of the glass of Murano was to the elaborate chandeliers that formed so important a part in the decoration of the reception-rooms of a Venetian palace in the seventeenth century. In these the metal framework is completely hidden by a thick foliage, as it were, of glass—frequently of the opalescent calcedonio—amid which the tall wax candles spring up here and there. M. Gerspach extols the decorative value of these chandeliers:—‘Le soir, le lustre de Venise allumÉ est un rayonnement harmonieux sans reflets discordants; le jour, stalactite ciselÉe, il Égaye l’appartement comme une note claire et joyeuse’ (La Verrerie, p. 173).

In the eighteenth century the contorted forms, imitating leaves and flowers, were replaced by pendent discs of colourless crystal, cut, polished, and often facetted. Of these later chandeliers there is a splendid series, whether of Venetian origin or not I do not know, at Hertford House. Such chandeliers were known in England in the eighteenth century as ‘lustres.’^[158] They are above all numerous in German palaces, and most of the glass is probably of German or Flemish origin. But of the earlier type I cannot find a single example in any of our public museums.^[159] The manufacture, however, has been revived at Murano, and chandeliers of this class, with no claims to antiquity, may often be seen in private houses both at home and abroad. The spread of electric lighting has given a stimulus to work of this kind, for the corolla-shaped shades that so often accompany our incandescent lamps have, in most cases, obviously been modelled upon the glass of the old Venetian chandeliers.

The glass-workers of Murano were a conservative body; their work was based upon secret processes and rule-of-thumb formulas. The elaborate division into different arti or corporations, each governed by its separate mariegola, made it excessively difficult to introduce any radical changes into the methods of work. It is quite pathetic to observe the efforts of the comparatively enlightened governing body, the conservatori alle arti, who in the last years of the republic attempted to introduce the new processes that were revolutionising the glass industry in the north of Europe. We find reports signed by great names—Morosini and others—recommending the introduction of English machinery, and drawing up plans for the cultivation of the Salsola soda on the islands of the lagoons. Little attention apparently was given to the artistic side by these reformers. One of the last names in the long list of the Murano glass-makers is that of Giuseppe Briati, famous for the purity of his cristallo; he excelled, too, in the designing and the execution of the vetro di trina, and Lazari declares that much of the ‘lace glass’ in our collections attributed to the cinquecento belongs rather to him or to his school.^[160] Briati in 1739 was allowed to set up a furnace in Venice itself for the preparation of his cristallo, the first time for more than four hundred years that such a permission had been granted. It is of this Briati that we are told that his glass found a place on the credenza or buffet at the public banquets of the Doge, beside the gold and silver plate. This would appear to have been an innovation (see above, p. 203) introduced with the special aim of encouraging the declining industry. An exception was again made in favour of one Giorgio Barbaria, who so late as 1790, in the parish of the Gesuiti, manufactured bottles by a new English method. But as a French writer somewhat naÏvely puts it—‘ce genre ne prÊte guÈre À la fantaisie.’

Before this time the Venetians had yielded to the new fashion of the day, and were making cut and engraved glass more or less after German or Bohemian models. Of this class were the trionfi di tavola—trophies of glass for the decoration of the dinner-table—as well as the gigantic chandeliers known as ‘ciocche.’ To such productions the artistic work of the time appears to have been confined. Of the first there is a fine specimen from the Casa Morosini set out in the centre of one of the rooms in the Museo Civico at Venice. I have already mentioned the chandeliers of cut glass. They played an important part in a rococo interior.

After the occupation of Venice by the French in 1797, the Directory attempted unsuccessfully to transplant the manufacture of beads (marguerites) to Paris. It is significant that they regarded this as the most important part of the glass industry. The corporations or arti were finally abolished in 1806.

During the ensuing thirty years the manufacture of glass was at the lowest ebb. There was, however, a first revival about 1838, which is associated with the name of Bussolin. But it was the energy and skill of a lawyer from Vicenza, Antonio Salviati, with the financial assistance of certain English enthusiasts for the art, Sir Henry Layard and Sir William Drake, in the first place, that led, not long after the middle of the century, to the furnaces of Murano again turning out something beyond window-glass and beads.

From the technical side Venetian glass belongs essentially to the Mediterranean family—the art was possibly learned in the first instance from the Byzantine Greeks. But it is probably as a consequence of their intercourse with the coast of Syria, the old home of glass, that the Venetians acquired at so early a date a pre-eminent position as glass-workers. Like that of their predecessors, theirs was essentially a soda glass. What distinguished it was, above all, its total freedom from colour; the Venetians were the first, at least since Roman times, to make an absolutely clear white glass. This result they obtained not only by care in the selection of their materials, especially in the source of the silica, but also by an early mastery of the use of manganese, ‘the glass-maker’s soap.’ The Venetian glass excelled again in its working qualities, in the extreme ductility which it maintained through a wide range of temperature. This property was in a measure due to the large quantity of alkali which entered into its composition. On the other hand, this excess of soda has led at times to a rapid tarnishing of the surface, visible above all in our damp climate.

But it is to the works of the contemporary Italian writers that we had better turn for information on these practical points. These are of two classes:—1st, Works of some literary pretension which contain chapters on the glass of Murano for the information of the general public. 2nd, Technical treatises, consisting for the most part of formulas for the use of the glass-maker. To the first class belong Fioravanti’s remarks on mirrors, which we have already quoted. Biringuccio, the Sienese, in his treatise on les arts du feu (De la Pirotechnia, Venice, 1540), has a chapter on glass (Bk. II. cap. xiii.). He tells us that the Venetians made glass from the ashes of chali, an herb that grows in Syria and also near Magalone, in the south of France (the lagoons of Maguelonne, near Cette). In the place of this chali the ashes of fern or of the mysterious duznea may be used. One part of the lixiviated ash is mixed with two of the cogoli, the clear white pebbles found in the bed of certain streams. To these materials a small amount of manganese is added, and the whole melted in a reverberatory furnace to form a substance known as fritta, already a kind of glass, but ‘mal purgata.’ The glass furnace is then described in some detail: it is made to hold eight crucibles (conconi), each three-quarters of a braccio (say fifteen inches) in height. These conconi are made with terra di Valencia, and are first well dried and annealed over the fritting-hearth. We are told how, after melting in these pots, the viscous substance is collected at the end of a hollow rod of iron, turned and returned upon the marver to unite the mass together, and then by blowing down the tube extended to form a vesicle. This ‘vescicha’ is now whirled round the head of the workman to lengthen it, or it may be pressed into a mould of bronze (‘in un cavo di bronzo’). It is now transferred to another rod of iron (the pontella, though the word is not used), worked up in various ways, and cut with shears. The handles and feet are added, and the vessel may be decorated by enamelling or otherwise.^[161]

La Piazza Universale di tutte le professioni del Mondo, by Tommaso Garzoni of Bagnacavallo, was, to judge from the numerous editions issued, a very popular work in its day. The copy before me, not by any means the first edition, is dated Venice, 1585. It contains a chapter entitled ‘De Vetrari, o Biccherari, Occhialari e Fenestrari.’ The superiority of the glass of Murano, ‘luogo amenissimo e delitiosissimo presso a Venetia,’ he attributes to the saltness of the water, to the absence of dust, so detrimental to the work, and to the abundant supply of wood which gives a most beautiful and clear flame. Besides, it is only at Murano that they know how to prepare the soda with which the beautiful cristallo is made. That made from the herb ugnea (cf. the duznea of Biringuccio) or from fern, produces a yellow and brittle glass,—the inferiority of the potash glass is here indirectly indicated. Among the long list of the vessels made at Murano we find zuccarini a reticelli or a ritortoli, interesting as an early mention of lace glass. The word zuccarino, literally a basin for sweets, is used as a general name for covered bowls or dishes. We then have the account (already quoted) of the preparation of latticinio, and also of a glass made up of fragments of canne of various colours, a kind of millefiori, in fact. There is, he tells us, nothing imaginable in the world that these Muranese cannot make with glass—castles even with towers, bastions, walls, and cannon. ‘Come nell’ Ascensa di Venetia talvolta s’ È vista,’ he continues. This refers, I think, to the display of masterpieces of glass in the procession on Ascension Day.

Garzoni, we must remember, is in this book in the first place concerned with the various trades and professions of his time, and he takes us next to the occhiolari, the makers of spectacles, who ply their trade in the Merceria, and finally to the Finestrari or Vetriari, who with marvellous rapidity fit into frames of lead ‘certi occhi di vetro’ made at Murano. We see from this that the old bull’s-eye glass was still in general use.

I must now, in conclusion, say something of the other class of writers, those who, without any literary pretensions, claim to disclose the secret processes and formulas of the glass-workers. These men are the successors of Theophilus and of the compilers of the early alchemistic treatises of which I have spoken in a previous chapter. It is noticeable that not one of these men, as far as we know, was a Venetian; indeed in every case, if the writer is not a Florentine himself, it is from Florentine libraries and archives that his works have been extracted.

Cennini was essentially a writer of this class, but in his Trattato della Pittura there are only a few casual references to glass. The three little treatises found by Gaetano Milanesi in the Florentine archives, and published by him in 1864, are chiefly concerned with the preparation of glass for mosaics. They may probably be attributed to the first half of the fifteenth century, and we thus have in the recipes which fill these books the earliest documentary evidence for the composition of Venetian glass. I will quote from the first of these little works a section (xxiii.) which treats of ‘the placing of glass on the surface of glass.’ The writer, it should be noted, is concerned with the preparation of the piastre or slabs from which were cut the little cubes for mosaic work; this question of the various ways in which a leaf of gold may be included between two sheets of glass is one which has already interested us.

‘? The glass to be about as thin as an eye-glass. Cut the leaves of the gold to the length of the glass, and put the gold upon the glass with white of egg; then place above this gold the other upper glass, and dry the whole. Then put them in the small ovens (fornelli), and let them be on a level so as not to slope, in order that the glass may not run. When they have become red-hot, load them with an iron so that they may grow together and unite. Then place them over the arch of the fornacetta (probably the fritting-oven), and let them cool little by little.’

The next section treats of the preparation of lattimo bianco by calcining four parts of tin and two parts of lead, and then mixing the resulting powder with ten parts of Syrian soda. But as is the case with all the treatises of this class, the majority of the sections are concerned with the preparation of the various ingredients by means of which glass may be coloured—the colori da ismalti. The green and opaque red are both obtained from copper-scale, the purple and crimson from various mixtures of manganese^[162] (so spelt in the text), and the yellow either from iron-scale or from a mixture of resin and tartar. As for the fine blue—the zaffiro—it should be noted that the pigment employed is described as azurro da vetro,^[163] probably a preparation of cobalt—similar to what in later times was known as smalt—which the glass-workers obtained ready-made from Germany.

In the early sections of the third of these little treatises^[164] the preparation of the soda is described in some detail. Much importance appears to be attached to the frit, for the third section is headed ‘Questa si È la pratica di fare la fritta, ciÒ È li pane del cristallino. Nota ed impara.’ In the composition of this frit there enters not only soda and the white pebbles from the Tecino, but a considerable amount of gromma or tartar, a substance containing potash, and perhaps lime also.

The preparation of ‘calcedonio in tutta perfezione’ is next described, and I may note that the presence in it of salts of iron and copper, to say nothing of silver, mercury, and azurro, would point to some variegated mixture resembling the schmelz of later days rather than to the opalescent glass to which this name was subsequently given (cf. p. 206).

Of greater importance than any of these little treatises is the work that Antonio Neri published in 1612. In fact, having regard to the influence of this book on future writers on the subject, especially upon those who sought to make glass by Venetian methods in England and elsewhere, it may without doubt be given the premier place as the most important work that has ever appeared on the preparation of glass. We know very little of the author except that he was born in Florence towards the end of the sixteenth century, that he was a priest, and that he spent some time at Antwerp, where it would seem that his attention was first directed towards the manufacture of glass. When, after the death of the Grand Duke Ferdinand in 1609, the manufacture of the soft-paste Medici porcelain was abandoned, we are told that in its place glass-works were established at Pisa, and with these works we may perhaps connect Neri’s little treatise. I have, however, already gone over most of the ground covered by this book in my quotations from Biringuccio and others, and I will postpone the consideration of what little further is to be gleaned from it until I come, in the account of our English glass, to speak of the translation of Neri’s book made by Merret in 1662.