PLASTER 



6189 



PLATEN -HALLERMUND 



coarse stuff one part fat lime to 

 two or three parts sand, with a 

 pound of ox-hair to two cubic feet 

 of plaster. This coat is left with a 

 rough surface, on which intersect- 

 ing furrows are scratched with a 

 lath, to form a key for the next 

 coat (floating), which contains less 

 sand and less hair than the render- 

 ing coat, and is floated to an even 

 surface by means of straight edges 

 or of a Derby float a large flat 

 board with two handles at its back. 

 To get a true surface, a general 

 level is indicated by placing fillets 

 of plaster (screeds) at intervals 

 over the surf ace, the plasterer bring- 

 ing the intervening spaces to the 

 level fixed by the screeds. A smaller 

 float is then worked over the sur- 

 face, which finally is scratched with 

 a coarse broom of bristle or fibre to 

 give a hold to the setting coat, 

 which may consist of fine lime 

 plaster to which plaster of Paris 

 has been added, or, if a specially 

 hard and smooth finish is desired, 

 one of the numerous patent plas- 

 ters may be used. 



Decorative plastering the pan- 

 elling, covering, gilding, colouring, 

 and general enrichment of walls 

 and ceilings had become very 

 elaborate in Tudor and Jacobean 

 times, and in the late 18th century 

 Adam, Chambers, Nash, and other 

 architects designed rich effects in 

 plaster. Ornamental plastering 

 may involve the use of the casting- 

 box and the chisel ; but the legiti- 

 macy of cutting plaster is disputed, 

 on the ground that sharpness of 

 edge and outline is alien to the es- 

 sentially " fat and sleepy " charac- 

 ter of plaster. Wood or zinc moulds 

 are used in running cornices, and 

 other straightforward ornaments ; 

 but rosettes, festoons, cables, and 

 other irregular patterns must be 

 cast from modelled designs, from 

 which moulds are made in gelatine, 

 plaster, or wax. 



The form called sgraffito decora- 

 tion is obtained by placing a trans- 

 fer design on the second of two fin- 

 ishing coats, the first coat dark, the 

 other light, and scraping away 

 portions of the top coat to form a 

 pattern in slight relief. Pargeting 

 or parge work shows a raised pat- 

 tern. Rough-cast is work in which 

 the finishing coat is mixed with 

 gravel or coarse sand. In pebble- 

 dash small stones are thrown 

 against the final coat before it sets. 

 Plaster casts are often made to imi- 

 tate metal by coating with an elec- 

 tro-copper deposit. See Cement; 

 Mural Decoration ; consult also 

 Notes on Building Construction, 

 Part II, chap, ix, Rivington & Co., 

 1875; Plastering, Plain and Deco- 

 rative, W. Millar, 1897 ; The Art of 

 the Plasterer, G. P. Bankart, 1908. 



Plaster of Paris. Partly de- 

 hydrated calcium sulphate formed 

 by heating to 120 to 130 C. the 

 mineral gypsum, which then loses 

 three-fourths of its water of crystal- 

 lisation. On the addition of water 

 equivalent to that removed by 

 calcining, plaster of Paris re- 

 crystallises, and sets as gypsum. 

 It is sometimes added to ordinary 

 lime plaster to quicken the setting, 

 or by itself for forming delicate 

 mouldings and ornaments, or for 

 repairing plaster walls of ceilings 

 It sets very quickly. Heated to 

 194 and finely ground, gypsum 

 forms a hard flooring material 

 and is a component of many pro- 

 prietary flooring compositions. Its 

 name is derived from the extensive 

 deposits found near Paris. 



Plataea. Ancient city of Greece, 

 in Boeotia, on the N. slope of Mt. 

 Cithaeron. Leaving the Theban 

 league, Plataea became an ally of 

 Athens, and sent 1,000 men to the 

 battle of Marathon. In the second 

 Persian War, Xerxes destroyed 

 the city at the instigation of 

 Thebes, 480 B.C. The Persian 

 army under Mardonius, with a 

 Theban contingent, fought the 

 allied Greeks under Pausanias of 

 Sparta before Plataea in 479. 



Pausanias was forced to with- 

 draw in some confusion, but rallied 

 his army, and the heavy armed 

 Greeks drove the Persians back 

 to their camp, which was stormed 

 with the aid of the Athenians, the 

 Persian army being almost anni- 

 hilated. This victory, following 

 upon that of Salamis, decided the 

 struggle. 



The independence of Plataea 

 was then guaranteed by the Greek 

 states, but in the Peloponnesian 

 War (q.v. ) it was besieged, 429- 

 427, and destroyed by Thebes 

 and Sparta. In 372 the Thebans 

 again destroyed it. See Greece. 



Plate (late Lat. platta, a thin 

 sheet of metal ; cf. Gr. platys, 

 flat). Word used in various deriva- 

 tive senses, all suggesting some- 

 thing thin and flat. In household 

 use, plates or platters were com- 

 monly made of'wood or pewter until 

 earthenware came into general 

 use. In engineering, iron or steel 

 plates are used in the construction 

 of boilers and the hulls of ships. 



In farriery the shoe put on a 

 racehorse is called a plate, and the 

 same word is also used for any 

 prize given in horse-racing with- 

 out any stakes provided by the 

 owners of the horses engaged. 



In photography, a plate is the 

 flat support, usually of glass coated 

 on one side with sensitive emul- 

 sion. When exposed to light, and 

 developed, it becomes a negative. 

 Ferrotype plates are used to 



secure collodion positives. In en- 

 graving, a plate is the metallic 

 surface on which the engraving is 

 done, and, by transference, the im- 

 pression from the engraved Plate. 

 Plate is a general term for gold or 

 silver articles, while the word is 

 also used in mineralogy and anat- 

 omy.and in heraldry, where it means 

 a roundel argent. See Electro-plat- 

 ing ; Photography ; Sheffield Plate. 



Plate. Name sometimes given 

 to the S. American estuary better 

 known as the Rio de la Plata, or 

 River Plate. See La Plata. 



Plateau. In physical geography, 

 a broad, flat, elevated region, or 

 raised plain. Plateaux or table- 

 lands may be classified as follows : 

 (1) Those built of accumulated 

 materials; (2) those produced by 

 the elevation of a former plain ; 

 (3) highland areas which have 

 been denuded to plateaux. Ex- 

 amples of the first type are found 

 in the W. Cordillera of N. America, 

 and in similar highland regions. 



The high plains, the famous 

 ranching lands, stretching from 

 Alberta to Texas, situated E. of the 

 Rocky Mts., are plateaux caused 

 by the uplift of the Rockies raising 

 the adjacent plains. They, like 

 similar regions E. of the Andes, in 

 S. America, and the Allegheny 

 Plateau W. of the Appalachian 

 Mts., are examples of the second 

 type. To the third class, i.e. pla- 

 teaux which are worn-down high- 

 lands, belong the Laurentian Pla- 

 teau of Canada, the Piedmont 

 Plateau E. of the Appalachian 

 Mts., the plateaux associated with 

 the ancient Highlands of Aus- 

 tralia and the Highlands of Scot- 

 land. The most extensive pla- 

 teau in the world is the continent 

 of Africa, for the whole of that land 

 mass, with the exception of the 

 extreme N.W. and S.W., is of this 

 type of relief. Owing to their ele- 

 vation, plateaux have a cooler 

 climate than neighbouring low- 

 lands, but they are frequently arid. 



Platelayer. Term used for 

 a man who lays and maintains the 

 permanent way of a railway. Such 

 men are so called from the type 

 of rail first used, which was known 

 as the plate rail. 



Platen (French, platine). In 

 printing, flat metal part of a press 

 that, by pressing the paper against 

 the type, makes the impression. 

 A platen machine is one that has a 

 flat as distinct from a cylindrical 

 method of impression. See Printing. 



Platen-Hallermund, ; COUNT 

 AUGUST VON (1796-1835). German 

 poet. He was born at Anspach, 

 Oct. 24, 1796, and entered Wiirz- 

 burg University in 1818, moving to 

 Erlangen in 1819. After 1826 he 

 lived chiefly in Italy, and he died at 



