ENTHASIS - n. Archit. A slight convex curve in a column shaft to correct the visual illusion that straight sides give of Curving inwards.
Alternate spelling ENTASIS (Mod L.f. Gk f. entino to strech)
The Concise Oxford Dictionary
Probably the first use of enthasis was in the construction of the Egyptian pyramids, but it can also be observed in Classical period Greek column designs, for example in the Doric-order temples in Segesta, Selinus, Agrigento and Paestum. It was only very rarely used in Hellenistic and Roman period architecture[citation needed]. The temples built during these periods were higher than those of the Greeks, with longer and thinner columns. Noted architects such as the Renaissance master Andrea Palladio also used it in their buildings.
The early Classical builders did not leave an explanation of their reasons for using entasis, and there are several differing opinions as to its purpose. Some descriptions of entasis [1] state simply that the technique was an enhancement applied to the more primitive conical columns to make them appear more substantial. Trevelyan believed that the effect represented strength by imitating the swelling of a strained muscle. [2] This accords well with the etymology of the word, from the Greek meaning 'to strain'. [3] This meaning could be related to the idea that entasis also serves to improve drainage on Greek horizontal stylobate.Another popular view, espoused by Hero of Alexandria, is that entasis corrects the optical illusion of concavity in the columns. [4] However, it does not explain the case of one well-known example, Paestum, where the entasis is so pronounced that it creates an obvious curvature, not an illusion of straightness. Conversely, in the Parthenon, the entasis is so subtle that it has almost no effect on the apparent shape of the columns, so is insufficient to correct any supposed illusion of curvature.An earlier and also lesser-known architectural practice was the application of a concave curve to the interior surface, symmetric to Entasis, and known as 'Ekstasis'. Dating to at least Mycenean time but perhaps before, an 'ekstatic' curve was believed to have a virtually magnetic power, quickly drawing those nearby into close proximity. Travellers have reported being subjected to Ekstatic effects in Hephaestus' temple in Aegina, in ancient Mystra north of Sparta, in the old temples atop Monemvasia, in the holy site now known as the church of St. Stephen near the tomb of Ptolemy II on Santorini (Thira) and in what is now known as Agamemnon's Tomb close by the ancient city of Mycenae.It has also been argued that a 'stunted cycloid' column that bulges in the middle is stronger than a column with straight sides. [5]
