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Blister  

Rupert Featherstone

Article

Bloom  

Rupert Featherstone

Misty surface coating that occurs on certain oil paintings with natural resin varnish films, especially of mastic. It diminishes the transparency of the varnish but can be removed in water. Bloom is apparently the result of atmospheric pollution. It is no longer a major problem, owing to the widespread use of synthetic varnishes....

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Technique described by Alexander Cozens (see Cozens family, §1) in his book A New Method for Assisting the Invention in Drawing Original Compositions of Landscapes (1786), whereby a blot or accidental mark can be developed and incorporated into a composition. Cozens’s title may have been inspired by Leonardo da Vinci’s description of a method of ‘quickening the spirit of invention’ by observing in damp walls and stones ‘strange landscapes’, ‘figures in violent action’, ‘expressions of faces’ and ‘an infinity of things’....

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Gordon Campbell

Local name of a blue fluorite (formerly known as fluor-spar) mined near Castleton, Derbys, since the mid-18th century. The name Blue John derives from the French Bleu Jaune (‘blue yellow’). It is a form of fluorite and was discovered as miners were exploring the cave systems of Castleton for lead. Banded Blue John fluorite has long been carved into ornaments in both England and France; its modern industrial uses include toothpaste. ...

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Board  

Jonathan Stephenson

Flat panel on which paper may be rested during drawing or painting, on which a painting or drawing may actually be executed (see also Panel painting), or on or with which a completed artwork is mounted. In these uses the board is of thin, rigid material such as natural wood or, more probably, processed and reconstituted wood or of a substance similar to or evolved from paper. Before c. 1700 artists were often depicted resting their work on a stout folder, but drawing boards are shown in use in the Drawing Academy (Segovia, Pal. Granja de San Ildefonso) by Michel-Ange Houasse, and a variant form with legs appears in Time and Death (1814; San Marino, CA, Huntington Lib. & A.G.) by Thomas Rowlandson. Since the 19th century, the commercial production of various types of boards has increased the range of potential supports. Millboard, a stiff card of pulp or paper sheets pasted together, frequently used in book covers and sometimes heavily impregnated with size, was used for oil sketching by ...

Article

Peter Cherry

Term used up to c. 1650 in Spain with reference to genre paintings; in modern Spanish it means still-life (see Still-life, §3). Sebastián de Covarrubias Horozco’s dictionary, Tesoro de la lengua castellana o española (1611), explains that a bodegón was a rough public eating-place where offal was consumed. Some Spanish genre paintings (see Genre) appear to be set in actual bodegones, the most notable being the Tavern Scene (untraced; see Jordan, p. 115) painted in Madrid by Juan van der Hamen y León, probably in 1627. However, by association, the work lent itself to a wide range of genre paintings depicting figures of humble origin, often with food and drink. As early as the 1590s Flemish and Italian kitchen and market scenes were referred to as bodegones in Spanish inventories. Such paintings were imitated by Spanish artists: three ‘bodegones de Italia’ were painted in ...

Article

Bole  

Rupert Featherstone

Fine red clay tinted with iron oxides to a red or yellow colour. When mixed with size, it is used as a base for gilding, since it takes a fine polish when burnished. It was widely employed on panel paintings up to the mid-15th century and is still used for picture ...

Article

Bone  

Frank Minney

The material that forms the skeletons of the higher animals. It consists of an organic portion composed mainly of the fibrous protein collagen and an inorganic portion formed by crystals of hydroxyapatite, a complex of tricalcium and calcium hydroxide. (For the identification of bone, see Technical examination, §VIII, 8.) The combination of these two substances forms a material that is light and strong, especially longitudinally. It is fairly flexible and possessed of reasonable cross-sectional strength. It is readily available as a by-product of butchery and is easily worked with simple tools. It can be sawn, scraped, carved, filed and glued. The size and structure of even the largest bones tend to limit their utility to small objects. These artefacts tend to be utilitarian in nature, though they may be decorated to some extent, and bone was often used to adorn objects made from other materials. Bone has sometimes been used as a cheap substitute for ivory, but it cannot be so finely worked, and the grain is more prominent. For tools it was often the preferred material because of its greater strength in small sections....

Article

Francis Woodman

A roof boss (Fr. bosse: ‘lump’, ‘knop’) is the block, or keystone, at the intersection of ribs in a rib vault (see Vault; for illustration see Section.). Particularly favoured in European medieval architecture, unnecessarily large blocks were used as a field for sculptural decoration, which both concealed the collision of the different ribs and their mouldings and provided additional dead-weight to assist in countering the thrusts engendered by the vaults themselves. Some Late Gothic English bosses are extremely large; those in the nave of Winchester Cathedral (c. 1440) and in King’s College Chapel (1513–15), Cambridge, weigh several tonnes each.

The first bosses consisted simply of the junction of the converging ribs. The earliest use of a central keystone in a rib vault occurs in the transept aisles at Winchester Cathedral (after 1107). A single block forms the apex of both intersecting arches, with a shoulder to receive each rib. Earlier rib vaults (e.g. ...

Article

Keith N. Morgan

Founded in 1867, the Boston Society of Architects (BSA) is the oldest of the three Massachusetts chapters of the American Institute of Architects, established in 1857. Dominated by Edward Clark Cabot as its president for the first three decades, the Boston Society of Architects reflected the nature of the expanding practice in the city at that moment. Opened in the same year as the BSA was the nation’s first academic program in architecture at the Massachusetts Institute of Technology (MIT). In addition to the MIT courses, the BSA was soon joined by the first substantial professional journal in the country, The American Architect and Building News, which began publication in Boston in 1876. The Society served as both a professional and a social organization in its early years, allowing members to meet and learn from their fellow practitioners. A parallel organization, open to non-architects as well, was the Architecture Association created in ...

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Article

Rupert Featherstone

Article

Stanislaus Fung, Chang Kyung-Ho and Mary Neighbour Parent

Roof support system composed of bearing blocks and bracket arms, and particularly associated with East Asia. The underlying structural principle—that bearing blocks may support more bearing blocks—can result in systems of great complexity.

The Chinese bracket system is a complex of timber bearing blocks (dou) and arms (gong), arranged in distinct sets and placed either on top of a column or on a beam joining the tops of columns. The bracket system helps to transfer the weight of the roof frame to the network of columns. The two basic elements of the system, dou and gong, were used as early as the first millennium bc in elementary forms of bracketing to bear the weight of the eaves, beams and rafters. By the Tang period (ad 618–907) these elements were combined with the Cantilever (Chin. ang), which made possible wide, overhanging eaves to protect the woodwork and rammed-earth (...

Article

Brick  

Margaret Henderson Floyd, Martin D. P. Hammond, Anthea Brian, Nicholas J. Moore, Yves Calvet, Robert Ousterhout, David Kennett, Jonathan Bloom, Margret Carey, Michael D. Willis, Sian E. Jay, David M. Jones, David H. Kennett, Robert Noah, G. Berends, Terence Paul Smith, Maria Brykowska, Sheila S. Blair and Jonathan M. Bloom

Small, regular-sized unit, usually of clay but also of calcium silicate (sand and lime) or concrete, used as a building material.

See also Conservation for Brick

Raw materials for bricks are widespread; the method of manufacture is determined by the physical and chemical properties of the clay and by economic circumstances. Calcium silicate bricks are made of a damp mixture of sand with 10% hydrated lime, formed in a powerful press and steamed in an autoclave for several hours. Concrete bricks (see Concrete, §II, 1) are made from a Portland cement and sand mixture cast in moulds. In the most common format the length is approximately twice the width and three or four times the depth. The size and weight of a brick are such that the bricklayer can pick it up in one hand, although sizes have varied over the centuries. Square blocks and thin, tile-like bricks have also been used. Bricks are used either in massive load-bearing structures or as a thin ...

Article

Bridge  

Ted Ruddock

Raised structure for passage over a declivity or obstacle. Until the advent of railways most important bridges spanned rivers, canals or sea inlets.

Bridges are classified by the traffic they serve (see Aqueduct; Viaduct) and by structural type. There follows an alphabetical listing and descriptions of bridge types. Cross-references within this article to this list are in the form ‘see Arch bridge’; cross-references to other sections of this article and to other articles in the Dictionary are in the usual form ‘see Arch.

Each span is an arch, a structure that thrusts horizontally as well as vertically on its supports (see fig.; see also Arch, §1). The common types of arch are as follows:

An alternative term for a tied arch (see below).

Commonly built of timber, metal or reinforced concrete and bearing columns that support a deck (for road, rail etc) above the crown of the arch (see fig. above (d)). An example is the ...

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Bronze  

P. T. Craddock

Alloy of copper and tin. In the West bronze was largely superseded by Brass, the alloy of copper and zinc, by the 5th century ad; many brass artworks, however, are commonly described as ‘bronze’. In early times Classical languages had just one term for copper and copper alloys, thus for example the Chinese had the word tang, the Tibetans li, the Greeks khalkos and the Romans aes. (For copper–zinc alloys produced by cementation (see Brass, §II) the Greeks had the term oreikhalkos and the Romans the related term aurichalcum, but these were not often used in general literature.)

The equivalent Anglo-Saxon general term was ‘brass’, and up to the 17th century this simply meant copper or one of its alloys. Various terms for copper–zinc alloys, such as latten and maslin, were in use in the late medieval and early post-medieval periods (see Blair and Blair, pp. 81–106). At about this time the term ...

Article

Brush  

R. D. Harley

A painting tool made up of a group of fibres bound and inserted into a handle. A brush should hold a quantity of paint and release it gradually as it is applied by the artist to make a consistent mark. The type of fibre, its length and the shape of the brush all affect the type of mark made.

See also China, People’s Republic of, §XIV, 4; Egypt, ancient, §X; and Japan, §XVII, 4.

Various brushmaking materials have been used over the centuries. In ancient Egypt macerated reed fibres were employed. Feathers and human hair have been used in East Asia, as have goat, deer, fox and wolf hair (although Sickman suggested that so-called wolf hair might in fact be that of weasel). The tail fur of the polecat, ermine, mink and sable (all varieties of Mustela) are mentioned in many sources as the best material for watercolour brushes. ...

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