An arch or similar structure built diagonally across the corner of a square building to support and act as a transition to a polygonal or round superstructure, normally a dome. Islamic architecture makes great use of squinch forms and a complex vocabulary of types evolved over the centuries.
Scholars have not reached an agreement on the origins of the squinch but it may well have originated in Sasanian Persia and been quickly assimilated by Late Imperial Rome: arched squinches are used in Sasanian palaces at Firuzabad at Qasr-i Shirin, and later become a characteristic of Byzantine buildings. A predilection for domed monuments, particularly funerary monuments, is notable in Islamic countries and led to the further development of the squinch as decorative element. Such monuments are divided internally into three horizontal zones: base, zone of transition, and dome. The zone of transition in the architecture of Iran and Central Asia from the 10th century to the 14th, where great innovations in squinch construction were made, typically comprised four blind arches alternating with four squinches. In many cases the zone of transition was a major focus of internal decoration, as in the Samanid mausoleum at Bukhara (see Bukhara, §II, A) and Tim (977–8). In the Bukhara tomb, the squinch areas are subdivided into two parallel arches buttressed by a half arch to create two concave segments per squinch corner, while the trilobed squinch makes its first dated appearance at Tim.
The trilobed squinch, with the profile of a shouldered or trilobed arch and interior subdivided into further concave arches, rose to prominence in the architecture of Iran in the Buyid and Saljuq periods, as at the Duvazdah Imam mausoleum in Yazd (1036–7) and the Friday Mosque at Isfahan (founded 771). It is a forerunner of the Muqarnas squinch, first seen in northeastern Iran, as subdivision of the squinch space into smaller and smaller concave arched components gave rise to the cascading tiers of muqarnas (see fig.). Muqarnas squinches, varying in complexity from the smoothly arching stone cells of the Firdaws Mosque at Aleppo (1235–6) to the extraordinary stucco honeycombs of the Alhambra Palacio de los Leones (c.1370–91), appear to be uniquely Islamic.
Squinch-net vaulting is another form of decoration used to make the transition from base to vault. The dome is supported by a network of squinches or pendentives of various shapes, divided by intersecting bands. This scheme was employed to great effect by Timurid architects at the Mausoleum of Gawharshad at Herat (1417–38), where the dome appears to be lifted upwards by the supports, an effect that is enhanced by the brightly painted fan-like forms on the squinches, pointing toward the dome itself. Closely related to the squinch-net vault are so-called “Turkish triangles,” which simplify the squinch into a vertical fan of triangular facets, as can be seen in the Karatay Madrasa in Konya (1251–2).
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L. Golombek and D. Wilber: The Timurid Architecture of Iran and Turan (Princeton, 1988)Find this resource:
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