Glass

by Edward Dillon

The bright green enamel by which on these cups the grass and the conventional trees are rendered, is perhaps the most characteristic colour of this quattro-cento ware. Note also on the wide-spreading foot the manner in which the gold is applied: in the use of this metal, if in nothing else, the Venetians surpassed their Saracenic predecessors. Here we have an early instance of gilding semé or broken up into minute irregular fragments. The gold appears to be incorporated with the glass; it must have been laid on at an early stage, for it lies scattered in detached fragments, and this is undoubtedly caused by the dragging of the glass, while still soft, during the process of manufacture. This manner of applying gold was used with great effect by the Venetians during the finest period—before and after 1500. Notice especially a little cup of thin white glass in the British Museum, on which the decoration is confined to a delicate powdering of gold of this nature.

Of the application of enamels of this class to a deep green ground, there is no finer example than the standing cup from the Debruge and Soltykoff collections (Slade, 361). This, too, is without doubt a Coppa Nuziale, and in the heads in the two medallions we may again recognise the bride and bridegroom. On a scroll by the latter head we read, AMOR VOL FEE—‘Love needs faith.’ The quaint head-dress of the woman calls to mind certain figures in Carpaccio’s pictures of contemporary Venetian life.

In the enamelled cups of this class the technical imperfections of the deep-coloured glass ground should be noticed. This is seen above all in the irregular outline of the margin. We have here a class of imperfection of quite a different nature from the tendency to collapse so often seen in large pieces of Saracenic glass. In the case of the Venetian glass the unevenness appears to arise from the imperfect fluidity of the metal when in the hands of the blower.

The date of this enamelled glass is fairly well fixed by the style in which the figure subjects are treated. The processions—the trionfi—are but rudely executed reproductions of those found on fifteenth-century marriage coffers, the heads in the medallions we meet with again on the contemporary mezza-majolica. Both may be seen in the woodcuts of the earliest printed books. We find the source of the gadroons and imbricated patterns in the repoussé forms given by the Venetians to their enamelled copper-ware.

There is somewhat more difficulty in determining the date of another class of Venetian enamelled glass. I refer to that on which the opaque enamels are painted with a brush upon a ground of thin colourless glass. In this decoration, especially in the conventional foliage, the drag of the brush loaded with the thin, somewhat intractable pigment, may often be clearly traced. There are some early examples of these ‘painted’ enamels which we may regard as the prototypes of a style of decoration on glass which soon obtained almost a monopoly among enamelled wares. We see the same technique and the same opaque colours on the French glass of the sixteenth century, and the faults are exaggerated and the palette even heavier in the case of the German glass of a still later time. We must seek the origin of this school in the Italian painters on majolica; on the other hand, in the eighteenth century the methods of the enamellers on glass no doubt influenced the decorators of porcelain both in Germany and elsewhere.

And here I may say that certain important technical difficulties, that must always have hampered the use of true transparent enamels on glass, have scarcely received the attention that they deserve. I mean the relations of the enamels, as regards the softening-point and rate of contraction on cooling, to the ground on which they rest. The question here is very similar to that which presents itself in the case of porcelain. Our present problem is, however, somewhat simpler, for with the latter material we have not only to consider the relation of the enamels to the glaze on which they lie (this takes, indeed, the place of our glass ground), but in addition the relation of the glaze itself to the porcelain body beneath must not be neglected.

The first condition for the successful application of an enamel is that it should be more fusible than the glass to which it is applied; not only that, but at the temperature at which the enamel fuses, the glass must still maintain its rigidity, otherwise the vessel on coming from the enameller’s stove will not preserve its original symmetry. It has been already suggested that the partial collapse so often observed in the large Cairene lamps may probably be explained in this way.

On the other hand, if the surface of the glass is not to some degree softened, there will be no intimate connection between it and the enamel, and the latter will be likely to scale off before long. This tendency will be increased if there is much difference in the rate or amount of contraction between the two materials. Difficulties of this kind long hindered the employment of certain fluxes and colours—that of cobalt, for instance, combined with a transparent flux. Such obstacles may, however, be surmounted in a measure, and the process simplified by employing (in place of a transparent lead flux) an opaque white, stanniferous enamel merely stained, in cases only externally, by a little colouring material. This apparently was the plan universally adopted by the Venetians in the fifteenth century, and it is here that their experience of the use of a similar enamel on copper may have served them.

One cannot but marvel at the technical dexterity so early acquired, and, alas! so soon lost by the Saracens, in the application of enamels to glass. The means by which they avoided the use of a lead flux in the case of their famous translucent blue, is above all worthy of admiration (see above, [Chapter X.]).

Certain defects which we note in the glass to which the Venetians applied their thick enamels may have been inseparably bound up with the use of these same enamels, and the impossibility of overcoming these defects may have been one of the causes of their abandonment and of the general adoption in their place of the painted decoration—mere thin skins of colour—which they were now able to apply to their white cristallo, the typical glass of Venice. After the commencement of the sixteenth century, indeed, the use of the solid enamels was almost confined to beadings and subsidiary ornament sparingly applied.