ntasis

Ntasis, more commonly rendered as entasis in English, is the deliberate outward curvature or swelling of a classical column shaft. The effect is intended to correct optical illusions that make a straight shaft appear to bend or taper too abruptly. In practice, the diameter of a column typically increases from the base toward the middle and may taper slightly again toward the top, producing a gentle convex profile.

The shaping of entasis is achieved by sculpting or casting the shaft so that its profile is not perfectly straight. The curvature is subtle, with the change in diameter amounting to only a few percent of the column’s height in many examples. The exact curvature varies with the column’s order (Doric, Ionic, or Corinthian) and with the architect’s desired visual rhythm, but the goal remains to harmonize perception of slenderness and mass.

Historically, entasis is a hallmark of Classical Greek architecture and is notably applied in temples such as the Parthenon. It was adopted by Roman architects and later by Renaissance designers who revived classical orders, sometimes adapting the technique to different materials and construction methods. The concept continued to influence neoclassical and modern interpretations of column design as a standard tool for achieving visual balance.

In contemporary practice, entasis is often analyzed with digital modeling and precise surveying to optimize aesthetics and structural performance. While profiles are not standardized today, the principle persists: a carefully proportioned convex shaft can enhance the perceived elegance and stability of a column.