Hellenistic Glass - Techniques

Techniques

Glass production of vessels or other glass objects was mainly of two distinct technological traditions, these of core-formed glass and mould-press or cast glass (Grose 1981).

• Core-formed glass: is the best represented and probably the earliest manufacturing technique applied. First, a core with the bottle’s shape was shaped around a metallic rod most probably by a combination of clay, sand, mud and/or animal dung. Then, molten glass was either trailed onto the core with the aid of a second tool or directly from dipping it into a container of molten glass. The surface was smoothed by continual re-heating and rolling on a flat slab. Finally, vessels were removed from the metallic rod, they slowly cooled down in a side chamber of the glass melting furnace and, then, the core material was scraped out of the interior. Common body colours were translucent dark or cobalt blue, opaque white, brown, red or olive-green and of the decoration opaque yellow, orange, white or turquoise trails in zigzag or feather patterns. This technique limited considerably the size of the vessels, which were mainly close vessels with thick walls.

• Mould-press or cast glass: it was first practiced by the Hellenistic glassworkers from the 3rd century BC onwards. Although different decorative results were achieved by variations in colours, the technique was virtually the same for mosaic, monochrome hemispherical bowls, transparent tableware and gold-sandwich vessels, both luxurious fine ware and more affordable types. Mould-press or cast vessels were mainly open bowls, shallow dishes and jars, but some closed vessels were produced as well. They were made from a single mould on which a piece of glass was slumped.

• Mosaic glass: vessels, namely bowls and plates, as well as inlays were produced with the mosaic technique. A multicoloured effect is achieved as a result of a variety of diverse cane configurations and colour combinations fused together and then slumped on an open mould.

• Network: a type of mosaic glass made of canes of spirally twisted glass threads of different colours laid side by side.

• Gold-sandwich glass: also found for the first time during the Hellenistic period. It technique consists of a ‘sandwich’ of two decolorized glass layers which enclose a sheet of gold leaf between them. The vessels were formed of two castings and they were carefully ground and polished.

• Cold-cutting: grinding and polishing by the application of stone-cutting techniques and by using harder materials, such us quartz. It was used as a supplementary technique to other processes as finishing and decoration.