West Clacton Reservoir, Great Bentley, Essex: Analysis of Glass Tesserae
Author(s): Kearns, Sarah Paynter
Two cakes of coloured glass and a selection of coloured glass tesserae were recovered from a site at West Clacton Reservoir, Dead Lane, Great Bentley, Essex. This coloured glass probably dates to between the mid-1st and mid-2nd centuries AD but analysis shows that it comes from a number of sources. The coloured glass was made by adding colourants and opacifiers to a transparent base glass. In most cases the base glass was a type of natron glass with a weak blue-green tint, also known as ‘self-coloured’. This glass was widely available in the Roman world since it was used for vessels, such as tableware and bottles. The colours were produced using a variety of metallic ores in various combinations, which were mixed and pre-heated to make a colouring substance or ‘corpo’ that was then added to the base glass. The red glass and some of the green glass was made using a plant ash base glass. Many of the same types of coloured glass were used for enamelling and glass tesserae were used rarely in mosaics in Britain. However the fact that some tesserae had been shaped from the cakes, and the presence of transparent blue glass tesserae, found in mosaics but not in enamels, suggests that the West Clacton tesserae were intended for use in mosaics.
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