A parison is the initial gather of hot glass that has been slightly shaped or inflated on the end of a blowpipe. Glassblowers form this basic bubble by rolling the molten mass on a marver to cool its outer skin. This establishes a uniform wall thickness and temperature gradient, allowing the maker to control the expansion of the glass before blowing it into a mold or shaping it freehand.
Heard on the job
Keep rolling the parison on the marver until the skin sets up, or it will blow out unevenly.