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Cameo glass is worked in a furnace by a craftsman, then finely engraved so as to obtain bas-reliefs in opaque-white glass on a darker coloured background, generally blue. |
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The Roman craftsman immersed a blue-glassed or another coloured blown object in a crucible of opaque-white glass so as to obtain a white inside layer ('flashing' or 'dip-overlay'). |
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This was deduced from recent studies on Roman cameo glass and experiments in a furnace at the Corning Museum of Glass. Even Venetian glasshouses from as early as the 19th century followed this same process. |
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English glassworkers from the 19th century, by contrast, adopted the method of preparing a blown object of opaque-white glass and having opened it at one end, blowing the coloured glass inside. |
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The object was then given to the engraver who carried out the bas-relief with a roller and other tools. |
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Ancient cameo glass are abrased on the inside to make the wall thinner. |
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