It is chiefly in the form of imitation gems that specimens of the earliest Spanish glass have been preserved until our time,[104] although the characteristic of old Roman glass which is known in Italian as the lattocinio or “milk-white” ornament, in the form of a thread or line carried all over the surface of a vessel, remains until this day a common feature of the glass of Spain, besides being found in Spanish-Moorish glass-work.
Rico y Sinobas says that the rules for cutting glass by means of a diamond or naife (as it was once called) are embodied in a treatise titled El Lapidario, originally written (perhaps in the fourth, fifth, or sixth century) in Hebrew, and which was brought to Spain some two or three hundred years later. This treatise was translated into Arabic by one Abolais, who lived at some time previous to the thirteenth century, and subsequently (in the year 1248, and by command of Alfonso the Learned) into the Castilian language.
Mixed up with a great deal of fabulous and fantastic matter, this treatise contains instructive and interesting notices of the composition and the colouring of old glass, including that of Spain. One of such notices is the following. “Of the eleventh degree of the sign of Sagittarius is the glass stone, containing a substance which is a body in itself (sand), and another which is added to it (salt), and when they clean these substances and draw them from the fire, they make between the two a single body. The stone thus made (glass) has many colours. Sometimes it is white (and this is nobler and better than the others), or sometimes it is red, or green, or xade (a dark, burnt colour), or purple. It is a stone which readily melteth in the fire, but which, when drawn therefrom, turneth again to its former substance: and if it be drawn from the flame unseasonably, and without cooling it little by little, it snappeth asunder. And it receiveth readily whatever colour be placed upon it. And if an animal be hurt therewith, it openeth as keen a wound as though it were of iron.”
The treatise also describes a stone called ecce, which was used in glassmaking, saying that it was found in Spain, “in a mountain, not of great height, which overlooks the town of Arraca, and is called Secludes. And the stone is of an intense black colour, spotted with yellow drops. It is shiny and porous, brittle, and of light weight …; and if it be ground up with honey, and the glass be smeared with it and submitted to the fire, it dyes the glass of a beautiful gold colour, and makes it stronger than it was before, so that it does not melt so readily, or snap asunder with such ease.”
I have said that the power of a diamond to cut glass is referred to in the same work, which further tells us that this gem “breaketh all other kind of stones, boring holes in them or cutting them, and no other stone is able to bruise it; nay more, it powdereth all other stones if it be rubbed upon them …; and such as seek to cut or perforate those other stones take portions of a diamond, small and slender and sharp-pointed, and mount them on slips of silver or of copper, and with them make the holes or cuttings they require. Thus do they grave and carve intaglios.”
All these branches of glassmaking were therefore practised by the Spaniards from an early period of their history. This people were also familiar with the use of emery powder, of talc applied to covering windows, and of rock crystal. We read in the translation of Abolais that crystal at that time was “found in many parts, albeit the finest is that of Ethiopia. The substance which composes it is frozen water, petrified. And the proof of this is that when it is broken, small grains are discovered to be within, that made their entry as it was becoming stone (crystallizing); or again, in some of it is found what seems to be clear water. And it possesses two qualities in which it is distinct from every other stone: for when crystal is heated it receiveth any colouring that is applied to it, and is wrought with greater ease, besides being melted by fire; insomuch that it can be made into any shape desired; and if this shape be round, and the stone be set in the sun, it burneth anything inflammable that be set before it: yet does it not effect this by any virtue of its own, but by the clearness of its substance, and by the sunbeams which beat upon it, and by the roundness of its form.”
We seem to foreshadow here, clearly enough, the application of this substance to making glasses to assist the sight, especially when the author of the treatise adds that on looking through the crystal, the human eye discovers “details of the greatest beauty, and things that are secreted from the simple (i.e. the unaided) vision.”
Rico y Sinobas (who possessed a fine collection of antique glass, Spanish and non-Spanish) inclined to think that in the time of the Romans the finest and strongest glass, as well as the costliest and the most sought after, was that which was manufactured in Spain. In early times the chief centres of Spanish glass-making were situated in the heart of the Peninsula (where now is New Castile), in the neighbourhood of Tortosa, and in certain districts lying between the Pyrenees and the coast of Cataluña, though subsequently the practice of this craft extended through the kingdoms of Valencia and Murcia, and the valleys of Ollería, Salinas, Busot, and the Rio Almanzora, forming a zone which reached from Cape Creus to Cape Gata. Other regions in which the craft was introduced, apparently at a later epoch, were those of the Mediterranean littoral, Cuenca, Toledo, Avila, Segovia, and other parts of New Castile, as far as the slopes of the Sierra de Guadarrama. In the rest of the Peninsula there is not the slightest indication (excepting an obscure reference by Strabo, to vessels and receptacles of wax) that glass was made during the Roman domination of the country, either in Andalusia, Lusitania (Portugal), or in the northern regions of Cantabria.
Rico y Sinobas has described a Spanish glass-oven of those primitive times. He says that such as were used for making objects of a fair size consisted of three compartments resting one upon the other; the lowest cylindrical, to hold the fire and ashes, the next with a domed top, for concentrating the heat, and the third and uppermost, which also had a domed top, for holding the pieces of glass that were set to cool by slow degrees. The wall of the oven contained a number of openings, which served, according to the level at which they were situated, for controlling the fire, adjusting the crucibles, or extracting, by means of metal rods, the lumps of molten glass, previously to submitting them to the action of the blowpipe. The dimensions of such of these primitive ovens as have been found in Spain or Italy, are nine feet in height by six feet in diameter, and the material of which they are built is argil, of a kind insensible to heat, and carefully freed by washing from all foreign, soluble, or inflammable substances. The crucibles, which were fitted in the oven two, four, or at most six at a time, were of this argil also, wrought and purified with even greater care. Ovens and crucibles of a smaller size were used for making diminutive objects such as beads and imitation precious stones.[105]
Almería was probably the most important centre of Spanish-Moorish glass-making, and is mentioned in connection with this craft by Al-Makkari. The oriental shape of the older vessels which were made in this locality is still preserved in certain objects such as jars, bowls, flasks, and aguardiente-bottles, which are still manufactured, or were so until quite recently, throughout a region extending from Almería to the slopes of the Alpujarra. “All these objects,” says Riaño, “are decorated with a serrated ornamentation of buttons, trellis-work, and the lines to which I have already alluded, which were placed there after the object was made, in the Roman style. The paste is generally of a dark green colour, and when we find these same features in vessels of clear white glass, we may affirm that they are contemporary imitations made at Cadalso or elsewhere, for they are very seldom to be met with in the provinces of Almería and Granada, and are generally found at Toledo and other localities; it is, moreover, a common condition of oriental art that its general form complies with a geometrical tracery, and we never find, as in Italian works of art, forms and capricious ornamentations which interfere with the symmetry of the general lines, and sacrifice them to the beauty of the whole.”