Glassblowing is an ancient technique that is used to shape heated, molten glass into aesthetic and functional objects such as vases, bowls, plates, candlesticks, cups and more. Glassblowers use a long blowpipe to shape the glass while it is still extremely hot. Glassblowing is a highly technical art form that requires specialized training and skill. Learn to recognize hand-blown glass by looking for certain characteristics.
A pontil mark, also called a pontil scar or a punt mark, is left on a piece of hand-blown glass when the glassblower removes the working rod or "pontil iron" from the glass object. Machine-made glass objects do not have these revealing marks. You'll usually find the pontil mark on the bottom of a vase, jar, plate or cup, but the mark may be hidden on other glass objects. Some glassblowing studios use pontil irons with their own distinctive symbols on the end, allowing them to turn the pontil mark into a sort of logo on each hand-blown piece. Simon Pearce, for example, marks each piece with a small circle of four petal-like forms.
Hand-blown glass does not have the machine-made symmetry and precision of manufactured, machine-produced glass objects. A hand-blown glass piece may have slight imperfections, irregularities, or even a slightly asymmetrical form. If you purchase a set of plates, glasses or other dishes from a glassblowing studio, expect each piece to look slightly different. These irregularities reveal that a human hand produced the pieces, rather than a machine. Slight irregularities of shape give hand-blown glass its distinctive charm, though some glassblowing studios set aside their most irregular or imperfect pieces for sale at a lower price.
Many hand-blown glass objects contain small air bubbles inside the glass. These air bubbles can get trapped inside of the heated glass during the blowing process, and they remain in the finished piece. Some glassblowing studios promote air bubbles as an aesthetic feature of their pieces. However, machine-produced glass objects can also contain bubbles, so this characteristic is not unique to hand-blown glass.