One of the chief glories of the later Middle Ages in Western Europe is undoubtedly to be found in the stained glass windows of the churches. Theophilus early in the twelfth century had already made himself master of this art, which he regarded as essentially a French one. The preparation of these vitraux involved a knowledge of the process either of spinning the molten paraison or of opening out the cylinder of glass, both comparatively late developments of the art of glass-blowing. In the staining of the glass we know from extant specimens what splendid results were obtained.

The composition of the window-glass of the thirteenth century is in some ways remarkable. It contained as much as from 8 to 10 per cent. of alumina, which we must regard as replacing in a measure the silica, for this constituent falls to as low as 56 per cent., and we can hardly otherwise account for the high percentage of the other bases—14 per cent. of lime, 17 per cent. of potash, and often 3 or 4 per cent. of iron. The result was a tough, somewhat horny glass, hard to work in consequence of the short duration of the viscous stage during the cooling. This was one reason for the smallness of the gatherings, and the modest dimensions of the resultant discs. On the other hand, such glass resists the action of the atmosphere better than any made nowadays, and the large amount of potash present probably promoted the brilliancy of the colours. From the earliest times the blue colouring was given by cobalt, and this was never of a richer and purer tint than in the twelfth century; already in the thirteenth copper was added to correct a tendency to purple. The famous ruby red, which became rarer after the thirteenth century until in the seventeenth the secret was entirely lost, was produced by the partial reduction of a small quantity of suboxide of copper, but in this case the colour is only developed on reheating the glass. The more purplish tint given by a somewhat similar treatment with gold was not known to the mediÆval glass-maker.^[95] Manganese was of course the source of the purple—the colour was used for flesh-tints in the twelfth century! The green was made by a mixture of the Æs ustum or copper scale with a native oxide of iron, the latter often known as ferretto—of this the best came from Spain. Finally, the yellow was given either by the sesqui-oxide of iron kept well oxidised by the presence of bin-oxide of manganese, or (where the surroundings favoured a reducing action) by a mixture of sulphur and some sooty material which probably yielded an alkaline sulphide. But in the older glass the yellow colour was never very brilliant; at a later time a fine yellow was obtained by a cementation process from silver, which was applied as a chloride or a sulphide to the surface of the glass.

If I trespass beyond my limits to give this rapid summary of what is known of the colours of mediÆval window-glass, it is because much of it will be found applicable to the contemporary Oriental enamelled ware and to the later Venetian glass.

In view of the high technical skill thus shown in the colouring and working of the material, nothing is more remarkable than the almost total absence from our collections of any glass, using that word in the narrower sense, that we can classify as Gothic. We know, indeed, that during these centuries much glass was made in France, Germany, and Italy. But for one reason or another the material was not in favour for objects that had any claim to be regarded as works of art. And yet during all this time the few rare specimens of sculptured glass brought from Constantinople, or of enamelled glass from Egypt and Damascus, were highly prized, and it might well be thought that the skill and knowledge to rival these examples were not wanting in the West. Such was not the case, however; the monasteries had ceased to be centres of practical art industry,^[96] and the glass-makers had retired from the towns to the depths of the forests, where under the patronage of the local seigneur they built their glass-houses, moving on from one spot to another as the fuel became scarce.

On the condition of delivering yearly to their feudal lord a specified number of vessels, these glass masters appear to have been freed from further imposts, and indeed they soon began to claim special privileges. In France some of these grants or contracts have been preserved in local archives, and in them we have a source of information lacking in other Western countries. Perhaps the most significant of these patents is that granted in 1338 to a certain Guionet. The Dauphin of the Viennois conceded to this maÎtre de verrerie the right of taking wood when it suited him from parts of the forest of Chamborant, on condition that the said Guionet should furnish him yearly, for the use of the prince’s household, with the following pieces of glass:—240 beakers with feet, known as hanaps; 144 amphorÆ, 432 urinalia, 144 large basins, 72 plates, 72 plates without borders, 144 pots, 144 water vessels, 60 gottefles, 12 salt-cellars, 240 lamps, 72 chandeliers, 12 large cups, 12 small barils, 6 large vessels for transporting wine, and one nef. This was certainly an ample yearly supply even for a princely household. The practical, not to say homely, nature of most of the objects requisitioned is obvious. The gottefle, we should add, has been thought to correspond with the later German gutraf; it was in that case a vase with a long twisted neck, sometimes double, like a Persian sprinkler; it was perhaps used for oil.^[97] The nef, no doubt, was an imitation in glass of the well-known centre-pieces of silver in the form of a ship. The little baril is a form handed down from Roman times. In Provence, as early as the year 1316, we find mention in the inventory of the property of the Countess Mahaut D’Artois of ‘Grant plantÉ de pots de voirre et de voirres d’Aubigny et de Provence et d’autres paÏs et de diverses couleurs et bocaux et bariz’ (Hartshorne, p. 88).

We see by this how little ground there is for giving the credit of the introduction of the manufacture of glass into France to King RenÉ. We shall find, however, later on, that this great patron of the arts was one of the earliest to take an interest in the Venetian glass of the early renaissance, and to bring the Italian workmen into France.

The word verre, or in the earlier form voirre or vouarre, was used vaguely in France even in mediÆval times for any cup from which wine was drunk. This usage alone might be brought forward as a proof of the general prevalence of glass vessels at an early time. Modern French writers on glass cannot always escape the awkward expression ‘un verre de verre.’ In England, where the use of the word glass in this sense probably came in somewhat later, we find more than once in inventories of the fourteenth century the quaint combination, ‘un verre de glass.’ In France, however, the more frequent expression was ‘un verre de fougÈre,’ literally ‘a glass of bracken,’ and we have here a double metonymy. This association of bracken and glass may be frequently noticed in the old French writers.

Long after the introduction of the cristallo from Italy, there were many in France who preferred to drink from the old greenish glass; like the Germans of to-day, they declared that the wine tasted better. Even Boileau, late in the seventeenth century, talks of a man holding ‘un verre de vin qui rit dans la fougÈre.’

We see then what an important place bracken, feucheria ad faciendum vitrum, played in the old glass-works of France. Now glass made from fern-ashes must of necessity be of a very inferior quality, more so probably than that made from the beechwood ashes used from of old in Germany. The passage to the new methods would here be much more revolutionary than in the case of the latter country. This consideration may help to explain the fact that while the manufacture of potash glass survived and adapted itself to the new methods in Germany, it became in time quite extinct in France.

The chronicles and romances of the thirteenth, fourteenth, and fifteenth centuries have been carefully searched by French scholars to find references to glass. Some ambiguity arises from the vague use of the word verre, to which I have already referred. But when Joinville tells us how the Comte d’Eu, in a moment of expansion, ‘dressait sa bible le long de nostre table et nous brissoit nos pots et nos vouerres,’ we can probably accept the latter vessels as verres de verre.

In the royal inventories of the fourteenth and fifteenth centuries, above all in those of Charles V. and of his brothers the Dukes of Anjou, Berry, and Burgundy, where there is any mention of vessels of glass, it is almost without exception of verre de Damas or of verre À la faÇon de Damas that we hear. Quite an exception is the goblet de voirre blanc de Flandre, garny d’argent, that we find in an inventory of the possessions of Charles V., taken in 1379. Notwithstanding this, it is evident that the French kings at this time took much interest in the manufacture of glass. When hunting in the forests around Paris, they would turn aside to visit the furnace of one of these local makers of verre de fougÈre who already claimed the privileges of gentlemen. Thus early in the reign of Charles VI. we find an entry of a payment ‘pour don fait par lui aux voirriers, prÈs de la forest de Chevreuse, oÙ le roy estait alez veoir faire les voirres.’ This was at the beginning of the fifteenth century; later on, as we shall see, both King RenÉ and Louis XI. were patrons of the glass-makers; and yet it is doubtful if we have in our collections any examples of French glass which can be attributed to as early a period as the reign even of the latter king.

Of glass made in Germany before, say, the end of the fifteenth century, we know even less than of the contemporary production in France. Theophilus, it is true, tells us of the manufacture of sheets of glass from cylindrical manchons, and this was probably until the seventeenth century a specially German process; he describes, too, the manufacture of blown glass of simple forms. But from his time, or at least from the time of the pseudo-Heraclius a little later, to that of Georg Agricola in the sixteenth century, when we find the glass industry taking an important place in many parts of Germany, there is little direct evidence on the subject to bring forward.^[98] Apart, however, from a few insignificant little bottles, used as reliquaries (Plates XX. and XXI.), nothing survives from this time. On the other hand, when in the fifteenth century we come again upon evidences of contemporary glass in Germany and Holland, as above all in the pictures of the early Netherlandish and of the Cologne schools, we find a distinct form of goblet already established, the prototype, it would seem, of a famous shape that was able to hold its own at the time of the invasion of Italian glass in the sixteenth century. There is nothing in France, still less in England, corresponding to the rÖmer and its various kindred forms.

In one application of glass the Germans appear early to have acquired some skill. We may perhaps regard the thirteenth century as the time when the use of glass for mirrors of any size first became general; this may account for the frequent references to them in the literature of the time. As far back as 1250, the great Dominican encyclopÆdist, Vincent de Beauvais, states that the best mirrors are made from glass and lead (ex vitro et plumbo). A spiegel-glas is mentioned by a German writer as early as the end of the twelfth century, and by the end of the next century the mirror provided a frequent metaphor for the poets of the time. Thus Dante, in two passages in the Divina Commedia, speaks of ‘a leaded mirror.’ In the Paradiso (ii. 89) Beatrice declares that the rays of the sun are reflected from the moon—

and in the twenty-third book of the Inferno (25-26) Virgil says to the poet, ‘S’io fossi d’impiombato vetro—I should not more quickly receive your image than now my mind receives your thoughts.’ This double reference would seem to point to a recent discovery that had attracted Dante’s attention.

In the thirteenth and fourteenth centuries it would appear that although the German mirror-makers had to import the clear crystalline ‘metal’ from Venice, the Venetians attempted in vain to make mirrors on the German system. The difficulty, perhaps, was to prepare flat and even sheets of glass of any size, and this difficulty the Germans may have surmounted by means of the cylinder process described by Theophilus.

The Nuremberg mirrors, however, so famous at a later time, were of a different type. They were of spherical outline, cut directly from the paraison of the glass-blower; into this paraison a mixture of ‘piombo, stagno, marchesita d’argento e tartaro’ had been introduced before the vesicle was quite cool—so at least a contemporary Italian writer asserts. Such mirrors were set in painted wooden frames with broad margins. An example of one of these may perhaps be seen in Jan van Eyck’s famous interior in the National Gallery.

If now we turn to England, the record is even more meagre. Mr. Hartshorne, who has industriously brought together every reference he could find to glass^[99] in this country during the Middle Ages, is fain to confess that he cannot point to a single example of what is undoubtedly English glass made between the Norman Conquest and the time of our Tudor kings. References to its use in contemporary writers are much rarer than in France. The cuppa vitrea, which in 1244 Henry III. sent to his goldsmith, Edward of Westminster, directing him to remove the glass foot, to replace it by one of silver, and to mount the whole in silver-gilt, was probably of Oriental origin; nor can we even claim for certain as English the two humbler vessels belonging at a later time to his son, Edward I.^[100]

As to the three ‘verrers’ of Colchester who paid taxes about the year 1300, the distinction between vitrier and verrier does not seem to have been as sharp then as it is now; they may well have been makers of glass windows. It is more significant to find in Henry III.’s day a Laurence Vitrearius holding land at Chiddingfold in Surrey, still in the time of Elizabeth a centre for the manufacture of the native glass made of fern-ash and sand. Again, William le Verir of the same place is mentioned in a deed of 1301. But perhaps the strongest case is that of John Glasewrythe of Staffordshire, who in 1380 had a grant of house and land at Shuerwode, Kirdford,^[101] and there made ‘brodeglass and vessel’—that is to say, window-glass and hollow ware (Nesbitt, South Kensington Catalogue, and Hartshorne, p. 132, etc.).

I reserve what I have to say of the mediÆval glass of Italy—of the early Altarists and Muranists—until I have described the enamelled Saracenic glass which in some measure influenced it.

But before turning again to the East, I must not omit to mention certain applications of glass that found favour in Western Europe during the later Middle Ages; indeed, apart from the coloured windows, such objects constitute the only genre of glass that can distinctly be classed as Gothic. I group together here various devices by means of which a design or pattern was applied to the back of a small sheet of glass—in gold for the most part, but other colours were sometimes used. The plaque thus decorated was either fixed into a piece of furniture, or simply backed with some impervious material. In this somewhat indefinite group is included, on the one hand, what is in fact a kind of thin mosaic; on the other, something that passed into the variety of painted glass known in later times as verre ÉglomisÉ. What distinguishes all this class of decoration is that neither the colour nor the backing is fixed by any furnace process—it is scarcely to be regarded as an art du feu, and thus lies somewhat outside our subject.

Of the so-called Cosmati mosaics, where the little triangular pieces of glass are inlaid in marble or wood, we have a good example in the thirteenth-century shrine of the Confessor in Westminster Abbey. At the same period a more elaborate means of decoration was obtained by painting the backs of little plaques of glass with gold and colours, and fixing them on the panels of pulpits, on the frames of the painted reredos, or even on secular furniture. I have seen examples of church furniture thus decorated at Aachen and in the Norman churches of Southern Italy—a pulpit at Bitonto in Apulia is a remarkable example. But we need not go far to find a still finer specimen of such work: the Gothic framework of the retabulum that formerly was placed in front of the high altar in Westminster Abbey^[102] is decorated with bosses of glass paste cut or cast en cabochon, with casts of antique gems, and, above all, with little plaques of blue and purple glass backed with silver foil. On the upper surface of these glass plaques a design in gold, consisting of small medallions with animals and twining branches, stands out in low relief. The pattern, says Viollet-Le Duc (Dictionnaire du Mobilier franÇais, i. 338), was first painted on the glass with a mixture of red ochre, wax and turpentine, and over this, before it was dry, gold leaf was laid, the gold adhering only to the soft ground. The effect of this external decoration is heightened by the shadow which it throws upon the silver foil beneath.

In other examples, the pattern is painted in various colours under the glass, and a leaf of gold, pasted beneath the more or less transparent pigments, shows through here and there. In all these instances the crude colour of the gold is lowered in places by coatings of varnish.

But plates of glass, somewhat similarly decorated, may play an even more important part in the decoration of the backs of altars, especially on the spandrels in the lower arcades of the reredos. The decoration now becomes pictorial, and is often most carefully executed. Or, again, such a little glass picture may be detached and mounted in a frame to form a pax or baiser-de-paix, a bijou reliquary, or other small devotional object. In such cases the gold is applied to the back of the glass by weak gum, and the design traced with a pointed instrument somewhat in the manner of the catacomb glasses. The effect may be heightened in various ways by additional touches of pigment on the draperies, or by a glazing of colour for the flesh-tints; the colours are worked up with a resinous body, and silver foil in little plates and spangles is added in places; finally, over the back is laid a piece of tinfoil, and this is folded over the edges (M. Alfred AndrÉ, quoted by M. Molinier, Spitzer Catalogue, vol. iii. p. 54). The back of the plate is generally found to be protected by a kind of pitchy varnish; to fix this some application of heat was doubtless necessary, but in no case, I think, is the gold design in this late mediÆval work enclosed between pieces of glass which have been subsequently fused together.^[103]

We are here concerned only with the Gothic examples of this class of work, and of these the majority appear to come from the north of Italy—they are probably of Milanese or Venetian origin. There is often in these early Italian plaques a coloured backing under the gold, generally of a bright red, but sometimes of green or black, and this backing shows through in places. In the case of a very beautiful example formerly in the Spitzer collection, the design was drawn upon the central portion of a plate of flashed glass; although this medallion is only 51/2 inches in diameter, there is a distinct boss in the centre. That such a defective piece should have been chosen for this delicate work would go to prove the rarity of sheets of glass with even surface at this time.

In later days more colour was used in the decoration, but such work as the magnificent baiser-de-paix in the Louvre, which came from the chapel of the order of the St. Esprit, does not fall within our present limit of time.

The late Marquis Emanuele D’Azeglio devoted himself to collecting specimens of gilt and painted glass of all ages and countries. This collection, unique of its kind, he bequeathed to his native town of Turin, where it is now exhibited in the Museo Civico. In some of the earlier pieces, especially on one of Byzantine character—perhaps Muranese work of the end of the thirteenth century—the gold is laid down upon glass of very irregular thickness. There are a few examples of Gothic work of this character in the British Museum, at South Kensington, and in the collection of Mr. Salting.