GLASSITES 



3554 



GLASS-SAND 





Glass. The making of a bottle. 1. Molten glass at end ol blow-pipe. 4. Preliminary blowing, after which the glass 



is thrust back into furnace. 2. As withdrawn from furnace, when held vertically and placed in mould, 5, the sides 



of which are brought together by means of a foot-pedalit is blown into its final shape. The finished bottle, 3, after 



being cut from blow-pipe, is, 6, carried on a wire shovel to the annealing furnace 



Photct. Clarke & Hyde 



is drawn away by a " bait," and 

 is kept hollow and cylindrical by 

 air forced through the mandril. 



Formerly much glass-blowing 

 was done with comparatively 

 primitive tools, e.g. the blow-pipe, 

 a hollow iron rod, 4 ft. to 6 ft. in 

 length ; the pontil, a solid iron rod 

 for holding a vessel by a glass seal 

 attached to its base ; a shaping 

 tool, resembling giant sugar tongs, 

 with cutting instead of spoon ends. 

 Sheet glass is made in the fol- 

 lowing way : A large and heavy 

 bulb, expanded by compressed air, 

 and lengthened by swinging, is 

 opened at the end distant from 

 the blow-pipe. The cylinder thus 

 formed is detached from the blow- 

 pipe, and, when cold, is split longi- 

 tudinally, and placed on a flat 

 bed in a kiln, unrolled and spread 

 into a flat sheet. Plate-glass is 

 molten glass poured upon an iron 

 table, and spread and flattened by 

 the passage over it of a heavy 

 roller. Rolled plate is molten glass 

 ladled or caused to flow from a 

 tank, and caused to pass over and 

 under a series of iron rollers. 

 Many varieties of bottk - 

 table glass are made by air pres- 

 sure into iron moulds, built up of 

 sections, and hinged together. In 

 the case of light tumblers, wine- 

 glass bowls, and electric-light 

 bulbs, the inside of the mould is 

 painted with an oil and carbon 



paste, and the glass is turned 

 inside the mould, whilst it is bein^ 

 blown, to obliterate marks made 

 by the joints of the mould. 



CUT GLASS. Decorative cutting, 

 which requires great skill, is 

 effected by pressing glasses, when 

 cold, successively against the 

 sharpened edges of wheels of iron, 

 stone, and wood, revolving on 

 horizontal spindles, and fed re- 

 spectively with sand and Water, 

 and pumice, mixed with putty 

 powder and water. 



The foundation of the glass 

 technology society in 1917, and 

 the inauguration of a national 

 glass research association are in- 

 tended to put glass-making upon 

 a proper scientific basis. Another 

 influence was the opening, in 1915, 

 in Sheffield University, of a de- 

 partment of glass technology, 

 under Professor W. E. S. TurneV. 

 See Sheffield. 



Bibliography. Glass, A. Nesbitt, 

 1878; Principles of Glass Making, 

 H. J. Powell, 1883 ; Glass in the Old 

 World, M. A. W. Dunlop, 188:5; 

 Glass Manufacture, W. Rosenhain, 

 2nd ed. 1919; Old Irish Glass, G. 

 Stannus, 1!)20; Irish Glass, M. S. 

 D. Westropp, 1920 



Glassites. Scottish sect, 



founded by John Glas. He taught 

 that all Church establishments 

 were unscriptural, and that each 

 congregation should be self-govern- 

 ing and have the power to appoint 



its own ministers. The publica- 

 tion of his views in The Testimony 

 of the King of Martyrs, 1727, led 

 to his suspension by the synod of 

 Angus, and in 1730 he was de- 

 posed from the Ministry. He 

 founded several congregations, 

 better known as Sandemanians, 

 after one of the more conspicuous 

 elders, Robert Sandeman, son-in- 

 law of Glas. The sect adopted the 

 practices of community of goods 

 and abstinence from certain kinds 

 of food. 



Glass Paper. Sheets of thick 

 cartridge paper upon the surface 

 of which powdered glass is lixed. 

 Glass is broken in an iron mortar, 

 ground to powder, and graded ac- 

 cording to the coarseness of the 

 particles by passing through sieves. 

 The paper is prepared by coating 

 evenly with liquid glue, and, before 

 the glue sets, sifting the powdered 

 glass over the surface, shaking off 

 the superfluous powder. Glass 

 paper is used for smoothing the 

 surface of wood. 



Glass-sand. Minute fragments 

 of siliceous minerals, loosely held 

 together. Their commonest con- 

 stituent is quartz ((/.''.), which 

 with felspar makes up about nine- 

 tenths of the bulk. The brilliancy, 

 lustre, transparency, and hardness 

 of glass depend upon the nature 

 of the sand used. High-class 

 glass-sand needs a silica-percentage 



