GLASS. 



cut to melt it completely. When the 

 fusion has continued the proper time, the 

 furnace is allowed to cool a little. In this 

 state the glass is exceedingly ductile, and 

 will assume any shape, according to the 

 fancy of the workman. The vessels thus 

 formed must not be permitted to cool too 

 quickly, hence they are put into a hot fur- 

 nace, in order that the heat may pass oft* 

 very gradually ; this is called annealing. 



Glass is often tinged of various colours, 

 which is performed by mixing with it, 

 while in fusion, some one of the metallic 

 oxides. Thus blue glass is formed by the 

 oxide of cobalt; green by the oxide of 

 iron, or copper; violet by the oxide of 

 manganese ; red by a mixture of the ox- 

 ides of copper and iron ; purple by the 

 oxide of gold; white by the oxide of ar- 

 senic and zinc ; and yellow by the oxide 

 of silver, and by combustible bodies. 



We shall give now a detail ofthe manu- 

 al operations in the manufacture of glass. 



Glass-bloiving, the art of forming ves- 

 sels of glass ; the term, however, is exclu- 

 sively applied to those vessels which are 

 blown by the mouth. The operation is 

 exceedingly simple ; the workman has a 

 tube of iron, the end of which he dips into 

 a pot of melted glass, and thus gathers a 

 small quantity of glass on the end of it; 

 he then applies the other end ofthe tube 

 to his mouth, and blows air through it; 

 this air enters into the body of the fluid 

 glass, and expands it out into a hollow 

 globe, similar to the soap bladders blown 

 from a tobacco pipe. Various methods 

 are used to bring these hollow globes in- 

 to forms of the different utensils in com- 

 mon domestic use, and several tools ; the 

 chief part of these are represented in 

 PLATE-GLASS MAKING. 



The first and greatest ofthe glass-blow- 

 ers' implements is the furnace ; it consists 

 of two large domes set one over the other, 

 the lower one stands over a long grating, 

 (on a level with the ground) on which the 

 fuel is placed ; beneath the grate is the 

 ash pit, and a large arch, leading to it, con- 

 veys air to the furnace. In the sides of 

 the lower dome, as many holes or mouths 

 are made as there are workmen to make 

 use ofthe furnace, and before each mouth 

 a pot of melted glass is placed ; the pots 

 are very large, like crucibles, and will 

 hold from three to four hundred weight 

 of liquid glass; they are supported upon 

 three small piers of brickwork, resting on 

 the floor of the furnace. The form rever- 

 berates the flame from the roof down up- 

 on the pots, and they are placed at some 

 distance within the furnace, that the flame 



VOL. VI. 



may get between the wall and the pots. 

 The upper dome is built upon the other, 

 and its floor made flat by filling up round 

 the roof of the lower dome with brick- 

 work ; there is a small chimney opens 

 from the top of the lower dome into the 

 middle ofthe floor ofthe upper one, which 

 conveys the smoke away from it, and 

 a flue from the upper dome leads it com- 

 pletely from the furnace. 



The upper dome is used for annealing 

 the glass, and is exactly similar to a large 

 oven, it has three mouths, and in different 

 parts a small flight of steps lead up to 

 each. We now come to describe the 

 smaller implements. 



Fig. 1 and 2, is a bench or stool with 

 two arms a b at its ends, which are a little 

 inclined to the horizon ; the operator, 

 when at work, sits upon the stool, and lays 

 his blowing tube d across the arms, as 

 shown in the figure. 



Fig. 3, are a pair of shears, or rather 

 pliers, formed of one piece of steel ; they 

 have no sharp edges, and spring open 

 when permitted ; the workman has seve- 

 ral of these of different sizes, which 

 are hung upon hooks ate in the stool, 

 fig. 4. 



Fig. 4, is a pair of compasses to measure 

 the work, and ascertain when it is brought 

 to the proper size ; the workmen should 

 have three or four of these. 



Fig. 5, a common pair of sheers, for cut- 

 ting the soft glass. 



Fig. 6, a very coarse flat file. 

 Fg. 7, is the blowing pipe ; it is simply 

 a wrought iron tube, about three feet 

 long, at x it is covered with twine, to pre- 

 vent it burning the workman's hand. 



Fig. 8, a small iron rod, of which there 

 should be several. 



Fig. 9, is a stool with a flatplate of cast 

 iron laid upon it, and/is another flatplate 

 upon the ground behind the stool. 



To explain the use of these tools, vre 

 shall describe the manner of forming a 

 lamp or urn of glass, Fig. 10, with a wide 

 mouth at top and a small neck^ at bot- 

 tom, through which the candle is inserted, 

 and which is fitted into a brass cap to sup- 

 port the lamp by. 



The operation is conducted by three 

 workmen. The first takes the blowing 

 pipe 7, and after heating it to a red heat 

 at the mouth of the furnace, dips it into 

 the pot of melted glass, at the same time 

 turning it round, that it may take up the 

 glass, which has then much the consist- 

 ence of turpentine ; in the quantity of 

 metal he is guided by experience, and 

 must proportion it to the size ofthe ves- 

 sel to be blown ; he then brings it from the 

 C 



