An Evaluation of the Variables that Contribute to the Quality of Punty Scar

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In glassblowing, a glass object is often transferred from the blowpipe onto a secondary rod for further shaping using a gob of glass known as a punty. The punty forms the connection between the glass object and the rod. After the vessel is finished it is removed from the rod by fracturing the punty. If performed correctly the fracture surface, or “punty scar,” left on the vessel is relatively small and ideally flat. To develop the skill and knowledge necessary to routinely form an ideal punty scar takes hours of dedicated work and practice by the glass blower. This study sought to define the parameters of punties that left the least amount of scarring on the glass vessel: this study-defined version of the ideal punty. Several variables were evaluated with regards to the average diameter of the punty scar, the average height of the punty scar, and the general shape of the scar. The factors recorded and analyzed included the difference in temperature between the punty and vessel upon their attachment, the thickness of the base of the vessel, the area of the jackline, the mass of the vessel, the approximate size of the punty, and the temperature of the punty when the vessel was removed. The data suggests that a smaller punty corresponds to a smaller diameter and height in the punty scar. While increasing the delta T and jackline area correlated with a slightly smaller height of punty scar, it also correlated to an increasing diameter of the punty scar. An increase in the thickness of the bottom of the vessel correlated with a smaller diameter of the punty scar but was unrelated to the height of the scar. The greater the mass of the vessel correlated with an added height to the punty scar.
Thesis completed in partial fulfillment of the requirements for the Alfred University Honors Program.
Honors thesis, Glassblowing, Glass, Punties