architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...

, entasis is the application of a

convex curve In geometry, a convex curve is a plane curve that has a supporting line through each of its points. There are many other equivalent definitions of these curves, going back to Archimedes. Examples of convex curves include the convex polygons, ...

to a surface for aesthetic purposes, or increasing strength. Its best-known use is in certain

orders Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * H ...

of Classical

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...

s that diminish in a very gentle curve, rather than in a straight line as they narrow going upward. The human eye would believe that the middle of the column was diminishing in a concave curve halfway up the column, and entasis corrects this.

Etymology

The word we apply to the design principle is used by the Roman architectural historian

Vitruvius Vitruvius ( ; ; –70 BC – after ) was a Roman architect and engineer during the 1st century BC, known for his multi-volume work titled . As the only treatise on architecture to survive from antiquity, it has been regarded since the Renaissan ...

, and derives from the Greek word έντείνω (''enteino''), "to stretch or strain tight". Creating the illusion of greater strength or perception of height may have been an objective in the application of entasis.

Examples

Examples of this design principle may be found in cultures throughout the world, from ancient times to contemporary architecture. The first use of entasis is probably in the Later Temple of Aphaia at Aigina, in the 490s BC. It may be observed among Classical period

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

column designs, for example, in the

Doric order The Doric order is one of the three orders of ancient Greek and later Roman architecture; the other two canonical orders were the Ionic and the Corinthian. The Doric is most easily recognized by the simple circular capitals at the top of t ...

temples in

Segesta Segesta (, ''Egesta'', or , ''Ségesta'', or , ''Aígesta''; ) was one of the major cities of the Elymians, one of the three indigenous peoples of Sicily. The other major cities of the Elymians were Eryx and Entella. It is located in the no ...

Selinus Selinunte ( , ; ; ; ) was a rich and extensive ancient Greek city of Magna Graecia on the south-western coast of Sicily in Italy. It was situated between the valleys of the Cottone and Modione rivers. It now lies in the of Castelvetrano, b ...

Agrigento Agrigento (; or ) is a city on the southern coast of Sicily, Italy and capital of the province of Agrigento. Founded around 582 BC by Greek colonists from Gela, Agrigento, then known as Akragas, was one of the leading cities during the golden ...

, and

Paestum Paestum ( , , ) was a major Ancient Greece, ancient Greek city on the coast of the Tyrrhenian Sea, in Magna Graecia. The ruins of Paestum are famous for their three ancient Greek temples in the Doric order dating from about 550 to 450 BCE that ...

. It was used less frequently in

Hellenistic In classical antiquity, the Hellenistic period covers the time in Greek history after Classical Greece, between the death of Alexander the Great in 323 BC and the death of Cleopatra VII in 30 BC, which was followed by the ascendancy of the R ...

and

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of Roman civilization *Epistle to the Romans, shortened to Romans, a letter w ...

period architecture. The Roman temples built during these periods were sometimes higher than those of the Greeks, with longer and thinner columns. Chinese carpenters of the

Song Dynasty The Song dynasty ( ) was an Dynasties of China, imperial dynasty of China that ruled from 960 to 1279. The dynasty was founded by Emperor Taizu of Song, who usurped the throne of the Later Zhou dynasty and went on to conquer the rest of the Fiv ...

followed designs in the AD 1103 Yingzao Fashi (Treatise on Architectural Methods or State Building Standards) that specified straight columns or those with an entasis on the upper third of the shaft. Noted architects, such as the

Renaissance The Renaissance ( , ) is a Periodization, period of history and a European cultural movement covering the 15th and 16th centuries. It marked the transition from the Middle Ages to modernity and was characterized by an effort to revive and sur ...

master

Andrea Palladio Andrea Palladio ( , ; ; 30 November 1508 – 19 August 1580) was an Italian Renaissance architect active in the Venetian Republic. Palladio, influenced by Roman and Greek architecture, primarily Vitruvius, is widely considered to be on ...

, also used entasis in the designs of their buildings. Entasis was often a feature of

Inca The Inca Empire, officially known as the Realm of the Four Parts (, ), was the largest empire in pre-Columbian America. The administrative, political, and military center of the empire was in the city of Cusco. The History of the Incas, Inca ...

walls and doorways to counteract the optical illusion that would make the openings appear narrower in their middles.

Concave curves

The opposite effect, applying

concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon A simple polygon that is not convex is called concave, non-convex or ...

curves in order to narrow surfaces that otherwise would appear to bulge, is also found in architecture, as in the sloping or battered walls of some

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

an and

Bhutan Bhutan, officially the Kingdom of Bhutan, is a landlocked country in South Asia, in the Eastern Himalayas between China to the north and northwest and India to the south and southeast. With a population of over 727,145 and a territory of , ...

ese monasteries and fortresses. The lower parts of such walls, approximately one third, have a slight concave or inward curve, while the higher parts retain an even slope, offsetting the outwardly bulging illusion created by a straight sloping wall. An example in Bhutan is the Dobji Dzong. When some collapsed walls of the

Punakha Dzong The Punakha Dzong, also known as Pungthang Dewa chhenbi Phodrang (meaning "the palace of great happiness or bliss"), is the administrative centre of Punakha District in Punakha, Bhutan. Constructed by Ngawang Namgyal, 1st Zhabdrung Rinpoche, in 16 ...

were rebuilt, around 1996, this asymmetry was not used.

In calligraphy

calligraphy Calligraphy () is a visual art related to writing. It is the design and execution of lettering with a pen, ink brush, or other writing instruments. Contemporary calligraphic practice can be defined as "the art of giving form to signs in an e ...

and

typography Typography is the art and technique of Typesetting, arranging type to make written language legibility, legible, readability, readable and beauty, appealing when displayed. The arrangement of type involves selecting typefaces, Point (typogra ...

entasis refers to the use of a concave curve to thin — rather than widen — the waist of a stroke or character. In calligraphy this is achieved either through a slight heightening of the pen or brush angle and/or by an increase in the speed of the stroke as it goes into a straight. Visually it is reminiscent of the structure of a bone and a stroke is seen as stronger for it. Entasis in a stroke is intended to counter the illusion a stroke with perfectly straight sides has of bulging slightly.

Origin in Greek columns

No record of the rationale for using entasis in columns by Classical builders has yet been discovered.. As a result, there has been extensive conjecture over its purpose. An early view, often articulated and still widespread, espoused by

Hero of Alexandria Hero of Alexandria (; , , also known as Heron of Alexandria ; probably 1st or 2nd century AD) was a Greek mathematician and engineer who was active in Alexandria in Egypt during the Roman era. He has been described as the greatest experimental ...

, is that entasis corrects the

optical illusion In visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide varie ...

of concavity in the columns that the fallible

human eye The human eye is a sensory organ in the visual system that reacts to light, visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and Balance (ability), keeping balance. The eye can be considered as a living ...

would create if the correction were not made. However, modern psychological research suggests that people do not actually experience any illusion that could be compensated by this design. Some descriptions of entasis state simply that the technique was an enhancement applied to the more primitive conical columns to make them appear more substantial. Other descriptions argue that the technique emphasizes the substantiality of, not the columns, but rather, of some other part or of the building while being viewed as a whole.

Yale Yale University is a private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the third-oldest institution of higher education in the United States, and one of the nine colonial colleges ch ...

architectural historian Vincent Scully argues that entasis emphasizes the weight of the roof of a building by making the building columns appear to bulge under the pressure distributed among them. Danish architect Steen Eiler Rasmussen believed that the effect represented strength by imitating the swelling of a strained muscle, a theory that accords well with the etymology of the word, from the Greek meaning "to strain". It also has been argued that a "stunted cycloid" column that bulges in the middle is stronger structurally than is a column whose diameter changes according to a linear progression, therefore, having a sound engineering purpose. Because their discussion of the application of the principle has never been discovered, it is unknown, however, whether the early Greeks knew this.Peter Thompson et al., "Entasis: architectural illusion compensation, aesthetic preference or engineering necessity?", Journal of Vision, Volume 7, Number 9, ISSN 1534-736

– abstract argues against traditional explanations for entasis and mentions possible engineering reasons

Literature

References

{{reflist Columns and entablature Optical illusions