Ein Artikel von D. Whitehouse und J. Price
(i) Forming the glass
Before the discovery of glassblowing, Roman glassmakers relied on two techniques perfected in the Hellenistic period: core-forming and casting. While core-forming lost ground very quickly, and was abandoned by about ad10, casting was widely used until the mid-1st century ad. The methods of casting employed by early Imperial glassmakers included making mosaic glass (millefiori) from sections of pre-formed canes, which were fused in a solid disc that was reheated and slumped over a mould. A similar technique was used to produce bowls decorated on the outside with vertical ribs. These were developed in the eastern Mediterranean in the late 1st century bc, and were made by impressing the pattern on a disc-shaped mass of molten glass that was then slumped over a mould. Other varieties of cast glass produced between c. 25 bc and ad 50 included ribbon mosaic glass, which consists of lengths (not slices) of canes arranged in geometric patterns, and gold band glass, which consists of strips of gold foil laminated between ribbons of colourless glass. The production of glass sculpture was noted by Quintilian (Inst. 2.21.9), and a few statuettes and parts of composite statues survive.
Strabo identified Alexandria in Egypt (Geography xvi. 756) and Sidon (Geography xvi. 758) as leading centres of glass production, and Pliny the elder claimed that glassmakers had been active for many centuries on the plain of the River Belus, 80 km south of Sidon (Natural History xxxvi. 191); indeed, he believed that glassmaking was discovered there. However, it is impossible to attribute specific early Roman cast vessels to any of these places with confidence. They may have been made in many places, both in the eastern Mediterranean and in Italy. Indeed, ribbed bowls were popular all over the Empire in the 1st century ad.
After the discovery of glassmaking, the most important event in the history of glass was the discovery that it can be blown. This simplified and speeded up the manufacture of glass vessels. Consequently glass ceased to be a purely luxury item, and glassware invaded the dining-rooms and kitchens of all but the poorest inhabitants of the Empire.
Glassblowing almost certainly originated in the Syro-Palestinian region in the 1st century bc. The earliest evidence of glassblowing consists of two finds in Israel: at Ein Gedi and Jerusalem. At Ein Gedi, a blown bottle was found in a cemetery that went out of use by 31 bc. In Jerusalem, excavations in the Old City revealed debris from a glass workshop. This included cast bowls, tubes and toilet bottles with splayed rims and shoulders, apparently blown with a blowpipe. Associated with the glass were nearly 100 coins, all of Alexander Jannaeus (reg 105-78 bc). The discovery of glassblowing, therefore, seems to have taken place in the first half of the 1st century bc. Despite its economic advantages over core-forming and casting, it did not replace the earlier techniques immediately; but by ad 50 it was the most commonly used method of making glass vessels.
Many of the earliest blown objects are small bottles used as containers for perfume. Among the other early forms made in the eastern Mediterranean are cups with two handles, the thumb-pieces of which are stamped with the maker's name (they include Artas, Neikon and Philippos) and the name of their home town, Sidon.
Although Roman glassblowers used a great variety of moulds, these fall into two well-defined groups: dip-moulds, which are cup-shaped objects used to shape (and sometimes decorate) the parison, which is then withdrawn and inflated to the desired size, and moulds with two or more parts, which are used to impart both the shape and the size of the body and bottom of the vessel, and can be opened to facilitate extraction. The earliest mould-blown glasses date from the first quarter of the 1st century ad and were probably made in the eastern Mediterranean, although mould-blown objects (some apparently made locally) have been found in contexts of similar date in Italy.
(iii) Decorating the glass
Glass vessels in the Roman world were decorated either by hot working or by cold working, or by a combination of the two techniques. Hot working includes processes such as fashioning pinched projections, or applying ornamental handles and bases, blobs, trails and other features, or blowing into decorated moulds, and was undertaken in the glass-house as part of the process of making the vessel. By contrast, decoration by cold working, such as painting and enamelling, or cutting and engraving, was undertaken after the vessel had been formed and carefully cooled, by craftsmen with quite different skills from those ot the glassmakers, and who did not necessarily work for the same establishment or even in the same geographical location as the glassblowers who produced the vessel.
(a) Hot working techniques
Blowing glass in a decorated mould was an important discovery because it meant that the vessel could be formed and decorated in the same process. This permitted the rapid production of large numbers of elaborate objects that are virtually identical.
Chips of glass were applied to the surface of vessels in the 1st century ad and either left in relief or marvered flush and enlarged by further inflation. In the 3rd to the 5th century objects were decorated with blobs dropped on to the wall while both the vessel and the
blobs were hot, so that the blobs fused with the walls. Two varieties exist: vessels with blobs of a single colour (almost always blue), and vessels with blobs of two or more colours. Vessels with blue blobs are found throughout the Empire; the other variety is wholly Western.
A large and heterogeneous group of objects have patterns trailed on to the vessel while it was hot, or with stamped appliqués. Usually, the decoration was dropped on the vessel from a gather on a pontil, after which it was either stamped or drawn out into linear patterns. Some patterns are simple, consisting of lines spiralling round the vessel; others, notably 'snake-thread' decoration, are complex.
(b) Cold working techniques
There are two types of painting on glass. In the first, the surface is decorated with watercolour, tempera or oil paint. This technique resembles painting on other materials and is known as 'cold painting'. In the second category, the paint consists of powdered glass, which is fused to the surface of the object by heating. This technique is known as 'enamelling'. The Romans practised both techniques (occasionally on the same object). Roman gilding on glass consisted of an application of gold leaf, rather than painting with liquid containing gold in suspension.
Decorative cutting and engraving was commonly employed on Roman glass. A small number of wheel-cut objects are decorated with openwork. Although such items are frequently known in modern literature as vasa diatreta, this term probably was not confined to objects made of glass and the expression 'cage-cup' is preferred. Cage-cups occur in several forms, the common feature being the presence of openwork, which may include a geometric 'cage', an inscription or a figured frieze. The glassworker cast or blew a thick-walled blank. After annealing, the blank was delivered to the finisher, who removed between half and two-thirds of the glass, leaving the openwork attached to the wall by small, well-concealed 'posts'.
(c) Hot and cold working techniques: cameo glass
Both hot and cold worked decoration sometimes occurs on Roman vessels of great luxury. Perhaps the best-known glasses showing this combination of decorative techniques are the late 1st-century bc - early 1st-century ad cameo-cut tablewares. Their basic shape was formed from two or more layers of glass in contrasting colours (often translucent dark blue inside and opaque white outside), and the outside layer or layers were then worked by cutting with hand tools and wheels to create elaborate patterns, in imitation of chalcedony and other hardstones. The cameo-cut forms include cups, bowls, jugs, amphorae and perfume bottles.
In the Hellenistic period, craftsmen produced cameos by exploiting the natural layering of certain types of stone. In Roman times, they also exploited the carefully contrived layering of glass objects. Gems and medallions apart, the Romans made cameo glass in only two periods: between c. 25 bc and ad 50 or 60, and sometime between the mid-3rd century and the mid-4th. Most early Roman cameo glasses are decorated in white on a blue background. We also find other colours, however, and some objects have more than one overlay. After the blank had been annealed, the decorator used hand tools and rotating wheels to carve, cut, grind and polish the surface. Decorating a cameo glass required not only expertise but also time. John Northwood's glass replica of the Portland Vase (completed in 1876; Corning, NY, Mus. Glass) cost him three years of concentrated effort.
2. Regional survey: western provinces
Italy and the other western Mediterranean provinces, together with Gaul, Germany and Britain, have produced a wide variety of fine Roman glassware belonging to various traditions of production and ranging in date from the late 1st century bc to the early 5th century ad. A few glass vessels are known before that time, chiefly in Italy, Iberia and southern Gaul, but most of these were imported either from western Asia or from the Aegean region. Away from the Mediterranean area, pre-Roman glass vessels are very rare apart from one or two late Hellenistic finds from settlements or burials.
Literary and pictorial sources from Italy began to indicate an awareness of glass beginning in the mid-1st century bc. Vitrum, the principal Latin word for glass, is first recorded at about this time by Lucretius (On the Nature of the Universe IV.145) and Cicero (For Rabirius Postumus xiv.40), and these references are followed by others in the later 1st century bc and early 1st century ad relating to properties of glass such as transparency, brilliance, brittleness, sharpness and the ability to magnify objects. At the same time, a series of representations of glass vessels containing fruits in water or coloured liquids was included in painted wall decoration, especially in houses at Pompeii and Herculaneum. These representations of forms in current production are also persuasive evidence that glass had captured the Roman imagination.
Archaeological evidence indicates that glass vessels came into common use in Italy during the later 1st century bc. Several factors combined to account for the great increase in the availability of glass, of which the most important was the invention of glassblowing in the 1st century bc, which completely transformed the production processes of vessels because of the rapidity of execution. It presumably also enhanced the appeal of glass because of the wide range of new forms attainable and the transparency of the material. Through blowing, glass also became available to a wide cross-section of Roman society, as some vessels were luxurious and highly decorated while others were everyday and quite plain.
Alongside the emerging Roman blown-glass industry there was a well-established cast-glass industry that had developed out of Hellenistic glassmaking traditions, and one of the production centres for this glass may have been set up in Rome. Both polychrome mosaic and brightly coloured monochrome cast tablewares were produced, some forms being developed only after the invention of blown glass. The products of both manufacturing traditions operated in the same markets in the late 1st century bc and early 1st century ad, but after the mid-1st century ad most polychrome and monochrome cast glass disappeared, and blown vessels completely dominated Roman glass production.
Glass production centres have been identified in many parts of the western provinces. Workshops are known at important cities such as Aquileia, Rome and Puteoli in Italy, Augusta Emerita and Tarragona in Spain, Lyon and Trier in Gaul, Cologne in Germany and London in Britain; and numerous others have also been found, though it is rarely possible to discover much about the forms of the vessels made in them. The vast majority of the vessels used in the western provinces was competently made everyday table and household wares with very few ornamental or decorative features, or simple containers. Most of these are likely to have been produced in glass workshops close to intended markets, though some, especially the containers, were traded over long distances. The following discussion concentrates on high-quality, decorated, luxury glasses.
(b) Glass with hot worked decoration
Blown vessels in bright colours, such as opaque or translucent blue, green, brown, yellow, red or purple, decorated with trails and blobs in contrasting colours, were a feature of the 1st-century ad Italian industry. These are particularly common in northern Italy and southern Switzerland, and they are likely to have been made in this area, perhaps at Aquileia and Lausanne, though they were traded widely, both to cities around the Mediterranean and on the Black Sea and to early military bases in the Rhineland and Britain.
Tablewares and unguent containers formed by blowing glass inside decorated clay or metal moulds occurred in many parts of the Roman world during the second and third quarters of the 1st century ad. Although most decorated mould-blown vessels are not of high artistic quality, they are often interesting in that they reproduce designs found on relief-decorated vessels in more expensive materials, such as silver or hardstone. Some of the designs are found throughout the Roman world, while others occur predominantly in the western provinces. For example, the finely modelled drinking cups bearing the name of Ennion are concentrated in Italy and the western provinces, and another well-known group of cylindrical cups with Latin inscriptions and scenes of chariot racing, gladiatorial combat or athletic contests is widely distributed in the western provinces but has not been found elsewhere. After the third quarter of the 1st century decorated mould-blown tablewares declined in popularity in the western provinces, and very few were made in the later Roman period.
The production of brightly coloured tablewares declined very rapidly when colourless glass appeared soon after the mid-1st century ad, and they had largely gone out of use by the end of the century. Thereafter, colourless glass was almost always preferred for tablewares, though not for household wares and containers, which continued to be made in naturally coloured bluish-green glass.
Some glass production centres established individual manufacturing styles that enable their most distinctive products to be recognized. For instance, a wide range of 2nd- and 3rd-century ad colourless vessels chiefly found in the middle and lower Rhineland and northern Gaul shows great virtuosity in hot worked decoration. Pinched-up and trailed decoration is common, especially the serpentine or 'snake-thread' trails in colourless, blue, green, opaque, yellow, white, red and gilded glass that were applied to the bodies of colourless vessels, and sometimes also to the rims, necks, handles or feet. Some trails were arranged randomly in curved patterns, while others were formed into leaf and tendril or leaf and garland motifs, or into birds or dolphins. Cologne appears to have been the main production centre of 'snake-thread' glass in the western provinces, though similar decoration may also have been produced in Italy or Spain, as well as in the eastern Mediterranean area.
The Cologne glasshouses also produced vessels with applied pre-formed ornamental motifs, including shells, birds and fishes. A small colourless convex bowl with a cracked-off and ground rim and a narrow wheel-cut horizontal line on the upper body is decorated in this manner. It has 18 pre-formed fishes and other sea creatures arranged in four rows around the body, the details of the fishes being outlined in bright blue glass. Two more bowls decorated in this way have been found in Cologne, and others have come from Trier and Rome. In addition, pre-formed fishes from broken vessels have survived in many parts of the Roman world, so other centres may also have produced such bowls.
(c) Glass with cold worked decoration
Painting and enamelling is not very common in the western provinces, though some cups and flasks have been recorded from Italy, Africa, Gaul, the Rhineland and Britain. Two groups of drinking cups are particularly noteworthy. A small number of early to mid-1st-century ad hemispherical cups, with painted and enamelled designs including motifs such as vine and ivy leaves, various birds and fishes, and pygmies and garlands on the outside surfaces of the body and base, have come from Italy, Africa, Gaul, the upper Rhineland and Britain, and were probably produced in northern Italy. One of the finest is the dark green example from a burial at Locarno-Muralto, which has a frieze of vine tendrils, ivy leaves and birds painted in blue, greyish-white, olive green, brownish-red, orange and yellow on the body and an eight-pointed star surrounded by a ring of dots painted in red and white on the base.
In the later 2nd century ad and 3rd another group of painted and enamelled cups is known. These are colourless and cylindrical and are concentrated in the lower Rhineland, northern Britain and beyond the Roman frontiers. They are generally decorated with scenes of fighting gladiators, or huntsmen and wild beasts, though representations of Bacchus and other designs also occur. When new these cups must have been brightly coloured and rather attractive, though weathering has now dulled the glass and decoration of most examples. It is apparent from the variation of the styles, the execution of the painting and the use of colour that the decoration was produced by more than one painter, and probably by more than one workshop. Many of the best-preserved pieces come from burials in Denmark, although they are thought to have been made and decorated in the lower Rhineland, probably at Cologne.
Gilded decoration is also unusual in the western provinces. A few late 3rd- or 4th-century cups and bowls with figured gilded decoration have been found in the Rhineland, especially around Cologne. Some show biblical scenes, such as the dark blue hemispherical bowl from Cologne-Braunsfeld (now in Cologne, Röm.-Ger.-Mus.) and the colourless bowl with bluish-green and dark blue blobs from St Severin, Cologne (now in London, BM). In Italy gilded decoration sometimes occurs on 4th-century vessel bases, mortared into the walls of niches in catacombs in Rome. The bases show a variety of designs including family portraits and Christian scenes.
By contrast with painted and gilded decoration, decorative cutting and engraving are commonly found on Roman tablewares. They came to prominence in the Roman world at the same time as the introduction of colourless tablewares, in the third quarter of the 1st century ad, and many different styles are recognizable in the western provinces from then until the early 5th century. In the later 1st century ad and early 2nd, truncated conical drinking cups are found widely in the western provinces and elsewhere in the Roman world. These are often decorated with areas of deeply cut facets arranged to produce diamond, hexagonal or irregular jigsaw patterns, while others have designs cut in relief; the latter are very occasionally undercut to form almost free-standing floral, leaf and other designs. In addition, a few pieces have engraved surfaces, and the same vessel form was occasionally decorated with painted or enamelled scenes.
From the 2nd century ad onwards various combinations of wheel-cut, abraded and engraved designs were produced on cups, beakers, bowls, plates, flasks and bottles, and some have been assigned to regional centres of cutting. In the 4th century in particular, a wide range of the high-quality wheel-cut and engraved decoration on colourless tablewares is found throughout the western provinces. Depictions of topographical, sporting, mythological and religious scenes were produced in many different styles by various combinations of facet and linear cutting, abrasion and engraving. Some of these, such as the series of shallow bowls with hunting, mythological, biblical and Christian scenes engraved freehand on the outside surface with a flint point and intended to be viewed from above, are concentrated in the north-west provinces and were probably produced in Cologne, while other styles are likely to come from workshops in Rome or Campania.
Perhaps the most extraordinary of the 4th-century ad vessels decorated by wheel-cutting are the cage-cups or diatreta. Many of these were made in colourless glass, though some, such as the cage-cups from Cologne-Braunsfeld (Cologne, Röm.-Ger.-Mus.) and Novara (Milan, Civ. Mus. Archeol.) in northern Italy, are colourless with bands of translucent coloured glass on the outside surface (red, yellow and green on the Cologne example, and green and blue on the Novara example). One or two others were made in a most unusual, apparently opaque, green glass that changes colour in transmitted light; the Lycurgus Cup (London, BM), a small deep bowl, decorated with scenes of the downfall of King Lycurgus at the hands of Bacchus and his followers, becomes translucent red, and a bucket-shaped cage-cup with handle from Tiermes in northern Spain (Madrid, Mus. Arqueol. N.) becomes orange. The precise function of many of these luxury vessels is not known, though the shallow examples may have served as spectacular hanging lamps, and the ones made in glass that changes colour would also have looked at their best with a light inside them.
(d) Glass with hot and cold worked decoration: cameo ware
Several of the rare and luxurious 1st-century ad cameo-cut tablewares are known in the western provinces, and it is very likely that some were produced in Italy. From Rome there is the Portland Vase (London, BM), an amphora with a broken base now repaired with a flat piece from another cameo-cut object, which is decorated on the body with very fine cutting showing six heroic or divine figures in two complex mythological scenes. Another amphora, complete with its pointed base, was found at Pompeii: this is the Blue Vase, which is decorated with scenes of cupids harvesting grapes and vine scrolls in the main figured zone, and a narrow frieze with sheep and goats among trees on the lower body (Naples, Mus. Archeol. N.). Other cameo-cut vessels were also found at Pompeii, including the Auldjo Jug, which has a trefoil mouth and high curved handle, and two decorated zones on the shoulder and body showing birds, vine tendrils and ivy and laurel sprays (London, BM) and a shallow bowl with saucepan handle decorated on the inside with Bacchic motifs (Naples, Mus. Archeol. N.). A more unusual combination of colours - translucent purple with opaque white - is seen on the jug decorated with a Priapic scene from Besançon in eastern France (Besançon, Mus. B.-A. & Archéol.).
The production of cameo-cut tablewares was revived in the 4th century ad, though very few pieces now survive. Unlike the early Imperial vessels, these used colourless glass for the inside layer and translucent brightly coloured glass for the outside layer. The segmental bowl from Stein am Rhein in Switzerland is the most complete surviving late Roman example of this technique in the western provinces. The dark red outer layer has been largely cut away to produce two scenes in relief of men hunting a bear and a panther, surrounded by an inscription in Greek letters reading 'drink and good health to you' in a ring below the rim. The inscription has been cut retrograde as it and the beast-hunting scenes were designed to be viewed from the inside of the bowl. In form, composition and style this vessel is closely comparable with the 4th-century bowls engraved freehand with a flint point described above, though it is not clear whether this was also produced in Cologne, or whether both the cameo-cut and the engraved bowls are simply presenting scenes commonly found in the late Roman art in the western provinces.
Quelle: D. Whitehouse - J. Price, Roman Glass, in: Grove Dictionary of Art
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