History of glass
Glass remained a luxury material, and the disasters that overtook Late Bronze Age civilizations seem to have brought glass-making to a halt. It picked up again in its former sites, Syria and Cyprus, in the 9th century BC, when the techniques for making colorless glass were discovered. The first glassmaking "manual" dates back to ca. 650 BC. Instructions on how to make glass are contained in cuneiform tablets discovered in the library of the Assyrian king Ashurbanipal. In Egypt glass-making did not revive until it was reintroduced in Ptolemaic Alexandria. Core-formed vessels and beads were still widely produced, but other techniques came to the fore with experimentation and technological advancements. During the Hellenistic period many new techniques of glass production were introduced and glass began to be used to make larger pieces, notably table wares. Techniques developed during this period include 'slumping' viscous (but not fully molten) glass over a mould in order to form a dish and 'millefiori' (meaning 'thousand flowers') technique, where canes of multicolored glass were sliced and the slices arranged together and fused in a mould to create a mosaic-like effect. It was also during this period that colorless or decolored glass began to be prized and methods for achieving this effect were investigated more fully.
Hellenistic glass
Core-formed glass vessels produced in the Mediterranean from 1525 to 50 BC were the most numerous and widespread. Core-formed vessels were generally small in size, opaque and designed to store perfumes, scented oils and cosmetics. The most common shapes were alabastra, amphoriskoi, aryballoi and lentoid aryballoi, oinochoai (jugs), and for the first time in the Hellenistic period hudriskai (three-handled flasks) and unguentaria (unguent bottles).
During the second half of the 3rd century BC, mosaic glass, also known as 'millefiori', literally, a thousand flowers, emerged. The group consists mostly of fused and slumped broad plates and shallow dishes with upright or out-splayed rims or hemispherical bowls. Sub-groups of mosaic glass production are 'network' or 'lacework' hemispherical bowls and vessels with meandering or spiral decorative patterns that imitate onyx. Often these bowls had a rim formed of a single ‘network’ cane of spirally twisted threads which gives a 'striped' effect. It is best represented in burial contexts from several large tombs in Canosa di Puglia (ancient Canusium) in Italy. They are open vessels since they are made with a mould but still opaque, like the widely produced core-formed vessels.