The glass itself is in all cases remarkable for the number of minute bubbles contained in it; in some of the lamps these bubbles are so numerous that the material is barely to be classed as transparent. In colour the glass varies from a pronounced bottle-green to an amber tint; it is more rarely of a greyish white. The size of many of the lamps and bowls must have necessitated the use of large melting-pots as well as considerable skill in blowing and manipulation. The irregular form so often to be observed in both lamps and vases is more likely to be the result of a partial collapse during the melting on of the enamels, than of any defect in the original piece as it came from the glass-blower’s hands.
In composition, to judge from the analysis of a fragment of a Cairene lamp made by Dr. Linke of Vienna (Schmoranz, p. 42), this Saracenic glass is essentially a normal soda-lime silicate with 69 per cent. of silica, 15·4 per cent. of alkali, and 8·6 per cent. of lime, thus far resembling the ordinary Roman type. The specimen examined, however, contained in addition to the lime as much as 4 per cent. of magnesia. As Dr. Linke points out, the presence of this last base would hinder the complete fluidity of the glass in the pots and make it difficult to get rid of the bubbles. But whether the presence of this earth in a single specimen is in itself sufficient to prove the non-Egyptian origin of these lamps as a class is another question. The fact that nearly one per cent. of manganese was found in this glass is of interest, as it shows that some attempt had been made to ‘cleanse’ the metal.
As regards the enamels on this Saracenic glass, we find that, with one important exception, they resemble generally in composition and character those employed at a later date by the Chinese in the decoration of their porcelain[[109]]—we have a readily fusible flux containing much lead coloured by various metallic oxides. The opaque red is given by oxide of iron, the green by oxide of copper, and the yellow by antimonic acid. The presence of this last substance is of interest: Dr. Percy found antimony in the glaze of Assyrian bricks, and I have taken for granted that it is the source of the yellow in the primitive glass of Egypt. The opaque colours, including the white, are probably produced by the addition of a little oxide of tin to the flux; Dr. Linke, however, does not seem to have found that metal in his analysis.
It is when we come to the blue, the dominant colour in this scheme of decoration, that a surprise awaits us. This colour, we should almost have taken for granted, would be derived from cobalt, for it is now recognised that at this time the use of that substance in the painting of earthenware (under the glaze) was prevalent in Western Asia. Dr. Linke, however, declares ‘that even the most subtle re-agents failed to discover any trace’ of either cobalt or copper in the blue enamel. For the grounds upon which he was able to attribute the origin of this fine blue to minute fragments of lapis lazuli, only partially dissolved in the flux, we must refer to the German chemist’s report. Now as ultramarine, the colouring matter of this mineral, contains a considerable amount of sulphur, some of it in an unoxidised state, it could not be used in combination with a flux containing lead, and indeed an analysis of the blue enamel proved it to be essentially of the same composition as the glass of the lamps; it contained, however, as much as 24 per cent of alkali, and this excess would ensure a slightly greater fusibility. It will be observed that the thick blue enamel on this Saracenic glass has considerable translucency as seen by transmitted light, but that the surface is always dull. In the British Museum is an admirably executed imitation of one of these mosque lamps, made as long ago as 1867 by M. Brocard of Paris. The blue, in this case cobalt, differs little in hue from that on the old lamps that stand beside it. It is, however, somewhat cruder in effect, and the surface is quite glassy.[[110]]
FLASK OF ENAMELLED GLASS
PROBABLY SYRIAN OR MESOPOTAMIAN. ABOUT 1300 A.D.
I come now to the scheme of decoration of this Saracenic glass. The important point to bear in mind is that the gold has for the most part disappeared from the surface. This gilding, however, played originally a most important part in the decoration. The fine lines of opaque red now so prominent were originally drawn with a free hand upon a detailed pattern of gold, with the object of accentuating the design. This gold brocading, when it is preserved, is of great beauty, especially that found upon the older pieces. Examine carefully the tall-necked bottle in the Slade collection: the body is covered with a fine arabesque of red lines, the pattern being made up of long-necked birds among foliage, and this appears poor in effect compared with the bands of rich enamel on the shoulder and neck. The effect, however, was very different at first when these dull red lines were carried over a rich ground of gold, of which traces only now remain here and there.
The gold, then, was applied first—at an early stage in the development of this family of glass it was perhaps the only decoration; the outline was then accentuated by means of red lines, and the coloured enamels then laid on in thick masses. We cannot say whether the colours were all melted on at one firing, for we know nothing in this case of the practical arrangements of the muffle-stove. On the exquisitely enamelled bottle from Würzburg in the British Museum ([Plate XXII.]), perhaps technically the most superb specimen of this class of decoration that has come down to us, the pinkish tint of the red and the manner in which it is gradated into the white, call to mind the use of the rouge d’or on Chinese porcelain of the eighteenth century; the green also of the conventional foliage is here shaded into the opaque white. The blue ground of the central medallion is of a brilliant turquoise, quite unapproached in other examples; the surface, however, of this blue enamel is in this case glassy and quite unlike the dead surface that we see on the mosque lamps. Are we to regard this opaque turquoise enamel as also based upon lapis lazuli, or rather as a soda-copper silicate?
As to the motives of the enamelled decoration—if figure subjects are absent from the mosque lamps, they are of frequent occurrence on the bottles and goblets: there we have polo-players and falconers mounted on horses, yellow, pink, and white; seated figures drinking and feasting or playing on musical instruments—always the same jovial, round-faced type; in only one instance have I noticed an elderly man with a beard. We sometimes find a frieze with dogs chasing stags and hares, or it may be a row of conventional lions. Birds are still more frequent—flying geese, as in the background of the hunting scenes, or long-necked herons forming part of the ornamental design of the field. Certain quaint little fishes with big heads and long fins, always of the same form, are not uncommon on the vases and cups; they are sometimes arranged herring-bone fashion; in one case, indeed, these little fishes are found on a mosque lamp.