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.
Engraving
However the use of glass engraving, usually using a wheel, to cut decorative scenes or figures into glass vessels, in imitation of hardstone carvings, appears as early as the first century AD, continuing into the fourth century CE at urban centers such as Cologne and Rome, and appears to have ceased sometime in the fifth century. Decoration was first based on Greek mythology, before hunting and circus scenes became popular, as well as imagery drawn from the Old and New Testament. It appears to have been used to mimic the appearance of precious metal wares during the same period, including the application of gold leaf, and could be cut free-hand or with lathes. As many as twenty separate stylistic workshops have been identified, and it seems likely that the engraver and vessel producer were separate craftsmen.