Glassmaking Technique: Roman Mold-Blown Glass

Free-blown glass vessels are shaped solely by inflation with a blowpipe and manipulation with tools. To make a simple bottle, molten glass is gathered onto the blowpipe, then rolled back and forth on a smooth surface, the marver, to give it a cylindrical shape. A small bubble is blown in the glass. The blowpipe is spun end-to-end in order to stretch the bubble out to form a long, narrow tube. The thick mass of glass at the end of the tube remains soft and is immediately inflated to form the vessel body. The bottom is flattened. To shape the bottle's mouth, a glass-tipped metal rod, the pontil, is attached to the bottom of the vessel. Drops of cold water are applied, and a sharp bang on the blowpipe causes the neck to break. After reheating, the opening can be reshaped. A gentle tap on the pontil easily breaks the finished vessel free. It can then be gradually cooled in an annealing oven.