Glass became one of the most prominent forms of artistic decor in architecture in the medieval Islamic world. Glassmaking was a skill regarded as the forte of artisans from Muslim lands, although unfortunately, it has been largely ignored by art historians.
Glassmaking
At the time of the Arab conquest in the seventh century A.D., glassmaking had flourished in Egypt and West Asia for over 2000 years. Artisans in these regions went about their business despite the momentous political, social, and religious changes taking place around them. Glassblowing, using molds, manipulating molten and its decorative application were techniques they had inherited from their Byzantine and Sasanian forefathers and perfected. And so, from the 7th to the 14th century, glass production in Muslim lands was both, innovative and glorious.
Blowpipes, five-foot-long iron or steel tubes, to gather, of molten glass, dip, and two- or three-part hinged molds, pontils, and wooden blocks, jacks, shears, and marvers were all that were needed to produce exquisite pieces, along with the dexterity and talent of the artisans of course.
Glassblowing was invented in the first century B.C. in the Syro-Palestinian region. It is what made glass much more widely and cheaply available, for previous methods of glass production were extremely labour intensive. Often overlooked in art history, from Cairo to Delhi, countless artisans anonymously produced glass objects which were indeed fit for a king. The three most prolific excavated sites that have yielded glass in the Islamic world are Fustat (Old Cairo) in Egypt, Samarra in Iraq, and Nishapur in northeastern Iran.
Mold Blown Decor Glass
Two types of molds were typically used in Islamic production. The first was a full-size mold. Molten glass at the end of a blowpipe was inserted into a two-part hinged mold in the shape of the vessel and then inflated. The pattern, carved on the interior walls of the mold, was impressed in relief on the glass upon inflation; the mold was opened to release the object. Popular patterns include vertical ribbing or fluting, honeycomb and chevron designs, a variety of geometric and vegetal motifs, and sometimes inscriptions.
The dip mold was also popular among Muslim artisans. Molten glass was inflated in a cylindrical mold in order to impress the pattern; the glass was then removed and further inflated outside the mold and tooled in a variety of forms to create the desired object. The subsequent inflation would make the pattern appear in a lower, less distinct relief than a pattern created using a full-size mold.
By its very nature, molded glass was duplicable to a certain extent, though the shaping and finishing details could produce a unique object. A mold had to be conceived, designed, and cast before a glass vessel was created. Most molds were probably made of bronze, though less durable materials may have been used. Thus, a metalworker was also involved in the process, making the chain of production more complex.
Cold-Cut Glass
Cold-cut glass objects can be divided into six broad categories. They may be scratch-engraved, faceted, with disks, with raised outlines, with slant-cut or linear decoration.
It quickly became a favourite, from Egypt to Iran, where the glass was cut and engraved with complex relief patterns created using mechanically operated wheels and drills to hair-width incisions made with a pointed tool. Linear, vegetal, and geometric patterns were common, along with Sasanian-inspired facet-cut decorations. Influenced by Roman tradition, cameo glass, colorless glass encased by a colored layer in order to create a dramatic bichromatic contrast was also amongst the popular types of relief-cut glass, in which the background and most of the inner areas of the main design were removed by cutting and grinding, leaving the outlines and some details in relief. The linear and the slant-cut styles were differentiated by a slight difference in the angle of the wheel’s approach to the surface.
Stained Glass
Painted glass objects were decorated with a brush or a pen after they had been crafted. Once the painting was done, they were reheated at temperatures that would fix the designs on the surface, without compromising the object’s shape.
It was produced in Egypt and Syria from the seventh through the ninth century, using copper and silver-based pigments. For a while, coloured glass did gain appeal, but people soon reverted to the classic monochrome shades. Silver-based paints first turn yellow, then turn amber followed by deep brown, whilst copper-based pigments quickly become red or ruby-colored, but their firing is difficult to control in a kiln. Yellow and orange stains can also be obtained from both silver and copper. In stained glass production, firing time and temperature control remain a challenge even today.
Mosaic Glass
Mosaic glass enjoyed a brief period of popularity in the Islamic world, in the eighth and ninth centuries in Mesopotamia and Syria. Most glass mosaic objects were unearthed at the site of Samarra, the capital of the Abbasid dynasty. What it was referred to back then, we do not know, but since the fifteenth century, it has commonly been known as millefiori (Italian for “thousand flowers”).
Although time-consuming, the process was not too complex. Individual roundels of differently coloured glass are arranged in a disk, heated, and slumped in a mold in the shape of the vessel. Upon cooling, the object is smoothed and polished. Islamic mosaic vessels are typified with a “bulls-eye” pattern, in which a large monochrome core is encircled by one or more rings; often, the outermost ring is formed by two alternating colors that fuse and create whimsical patterns.
Enameled Glass
Enameled and gilded glass are the best known and historically most treasured types of glass in Islamic art history. It developed in the twelfth century in the Syrian area. Production flourished in the thirteenth and fourteenth centuries under the Ayyubids and the Mamluks. The late fourteenth century saw a decline in production; by the early fifteenth century, dwindling patronage eventually caused workshops to close. By the late fifteenth century, the production of most enameled glass had shifted to Venice. It is likely that a combination of economic, political, and artistic factors caused the disappearance of enameled glass in the Islamic world.
In this decorative technique, gold and/or enamels (powdered opaque glass) were applied to a glass surface using an oil-based medium and a brush or a reed pen. Gild and individual enamel colors have different specific chemical qualities, which means different temperatures were required to permanently fix them on glass. However, applying colors one at a time and individually fixing them would subject a vessel to reheating several times and entail the risk of deforming its shape. In all likelihood, Mamluk glassmakers mastered a procedure in which they applied all the colors at once and fixed them during a single firing in the kiln without having them run into one another.
Hot-worked Glass
The objects produced in the hot-worked technique range in origins all the way from Egypt to Central Asia, whilst the timeframe spans from the seventh century to the thirteenth. It is a type of glass that is manipulated and decorated while the blown vessel is still hot and malleable and is subdivided into three categories according to the specific decorative technique.
The first of this kind are vessels with applied decorative trails, in which hot trails of glass were “poured” over the vessel while the inflated object, which was still attached to the pontil, was rotated slowly to form a spiral pattern along its body. Often, the trails were manipulated with a pointed tool or a fine pincer to create patterns. Such objects were produced mostly in Syria and Egypt from the tenth to the fourteenth century.
There were also works with impressed patterns where objects were decorated using metal tongs with circular or square ends that had a carved design on one or both sides. Most objects of this type are small bowls decorated with a limited range of geometric, pseudo-vegetal, and zoomorphic motifs and attributed to Egyptian workshops operating in the ninth and tenth centuries.
Lastly, there is glass with marvered trails, in which the trails were integrated into the blown vessel using a rotating motion against a marver (a polished stone or an iron slab) so that they became flush with the surface. The trails were tooled and “combed” with a toothed implement into wavy, arched, or festooned patterns. The trails are almost always white, providing a pleasant contrast with the usually dark-colored vessel. Glass with marvered trails was produced continuously in Syria and Egypt from the early Islamic period to the fourteenth century.
