blowpipe

A blowpipe is a hollow iron or steel tube, typically 4 to 6 feet long and 0.5 to 0.75 inches in diameter, used to gather molten glass from a furnace and shape it by blowing air through it. The glassmaker seats one end in the mouth (or in modern practice, connects it to a foot-operated air valve or compressor) and uses lung or mechanical pressure to inflate a bubble of glass at the working end. The tube must be long enough to keep the glassmaker's face away from radiant heat, which regularly exceeds 2000 degrees Fahrenheit at the gather point.

The working end of the blowpipe is routinely reheated in a reheating furnace (called a glory hole) to keep the glass workable; without this, the gather becomes too viscous to shape. As the glassmaker blows, they rotate the pipe steadily in both hands to distribute the glass evenly around the bubble and prevent sagging. The rate of rotation and the force of breath (or air pressure) directly control wall thickness and final form. Most production blowpipes have a slight taper and are turned down at one end to fit a mouthpiece (in hand-working) or to accept a pneumatic air line.

Hand-blown blowpipes remain the standard in art glass and bespoke tableware production, where the glassmaker's judgment and skill determine every dimension. Industrial glassware makers typically use mechanized versions: the pipe is mounted horizontally and fed by a gather machine, with compressed air replacing human breath and programmable timing controlling inflation pressure and duration. This removes the physical strain of sustained hand-work and improves consistency, though it sacrifices the intuitive control of traditional glassblowing.

The iron core of the blowpipe must resist thermal shock; cheaper pipes warp or crack after extended use. Properly made tubes have a smooth bore to avoid restricting airflow and prevent air pockets that cause weak spots in the bubble. After years of service, the internal surface becomes pitted and irregular, making it progressively harder to control inflation. A scored or cracked bore is a safety hazard, as compressed air can force its way out sideways into the glassmaker's mouth.

The term is old, appearing in English glassmaking records from the 16th century. Before the blowpipe, glass was formed by pontil (punty) work alone, where the artisan shaped the gather while it sat on the end of a solid iron rod. The blowpipe allowed formation of hollow shapes and remains essentially unchanged in principle from its medieval ancestors, which is rare in industrial tooling.