borsella

A borsella is a long-handled tool used to open or close the gap between two pieces of glass during hot working at the furnace. The tool consists of a handle, typically wood or steel, joined to a split or forked metal head that grips the glass without marking it. Glassmakers use it to adjust the spacing between gather points, separate fused pieces, or hold glass at a precise distance while shaping occurs.

The working end comes in several forms depending on the task. Some borselles have flat, parallel jaws that grip smoothly; others have slightly angled or curved contact surfaces to distribute pressure evenly across hot glass without causing thermal shock or fracture. The fork type, split vertically, spreads open to grip a single piece or the gap between two pieces. Length varies from 24 to 40 inches to keep the operator's hand at a safe distance from the furnace mouth, which typically operates between 2000 and 2200 degrees Fahrenheit.

Timing is critical when using a borsella. Glass must be hot enough to move without cracking, but if overheated it becomes too fluid to control. The tool works best on glass in what glassmakers call the "working range," where the material has enough viscosity to hold a grip but enough plasticity to respond to pressure. A common mistake is applying too much force too quickly, which can cause the glass to shatter rather than spread or contract.

The name borsella, also spelled borsellum or borsellus in older texts, likely derives from early Italian glassmaking vocabulary, though the etymology is uncertain. The tool is fundamental to traditional hand-gathering techniques and remains essential in studio glasswork and small-batch production. Industrial automated lines use heated pinch rollers or pneumatic spreaders instead, but the borsella is still found in every classical glass furnace shop.