glass-working lathes are similar in design to other lathes, but differ markedly in how the workpiece is modified. glass-working lathes slowly rotate a hollow glass vessel over a fixed- or variable-temperature flame. the source of the flame may be either hand-held or mounted to a banjo/cross-slide that can be moved along the lathe bed. the flame serves to soften the glass being worked, so that the glass in a specific area of the workpiece becomes ductile and subject to forming either by inflation ("glassblowing") or by deformation with a heat-resistant tool. such lathes usually have two head-stocks with chucks holding the work, arranged so that they both rotate together in unison. air can be introduced through the headstock chuck spindle for glassblowing. the tools to deform the glass and tubes to blow (inflate) the glass are usually handheld.