This glass vessel, known as an amphoriskos, was discovered in a tomb in the cemetery of the Phoenician trading colony at Tharros. Such bottles were common in the sixth and fifth centuries BC. They were made by core-forming, which was probably the earliest method used for manufacture of glass vessels and remained the usual way of making small vessels of various shapes until about the first century BC. A core of sand and dung was modelled into the desired shape, attached to a cane and dipped into molten glass, then rolled on a flat surface to obtain a smooth finish. Various techniques were used in decoration. The most common was the application of different coloured threads of glass, trailed around the vessel while it was still hot and molten. When the piece was finished and cooled the core was removed. There is no firm evidence for glass vessel production before the middle of the second millennium BC, and towards the end of that millennium glass production appears to have all but ceased. This perhaps reflects the general economic and political upheavals of the period. When glass is found at Near Eastern sites dating to the first millennium BC it is commonly identified either as Assyrian or, more commonly, as Phoenician, though in fact centres of production in Phoenicia have not yet been found. In the Mediterranean the main glass manufacturing centre appears to have been the island of Rhodes.