Air-twist stem

An air-twist stem is decoration in the stem of a drinking glass made by twisting columns of air inside the glass. Corning Museum of Glass records the type in eighteenth-century and later drinking glasses.

The spiral lies inside the glass

The air channels may form a simple or complex spiral as the stem is drawn and twisted. The decoration should not be confused with random bubbles. It also differs from opaque twist, where white or coloured glass threads form the spiral.

Examining an older glass

View the stem in good side lighting and record the full course of the spiral, the junction with the bowl and the transition to the foot. Air twist alone does not securely date a glass because the technique was copied later. Tool marks, pontil, overall form, repairs and documented provenance should be assessed together.

Sources: Corning Museum of Glass, Air twist and Corning Museum of Glass, Twist.