GLASS AND GLASS-MAKING 



PLATE-GLASS MAKING 



In the process of making plate glass, the last vestige 

 of picturesqueness, as seen in the older glass-blowing 

 establishments, is removed. Here there is no use for 

 the sturdy gatherer protecting his face with the mask 

 held in his teeth, nor for the muscular blower. Science 

 and mechanics have found better substitutes for brawn 

 and muscle in the form of machinery; and, as in so 

 many other cases, produce a superior product to that 

 made by manual labor. 



Plate-glass making is simply a kind of casting, very 

 similar to the casting of ordinary metals. The glass 

 is first melted and then poured upon a flat surface, 

 rolled to a certain thickness and allowed to cool. 

 When cool it is ground and polished. 



Naturally, the materials for making plate glass must 

 be carefully selected. Only the finest quality of white 

 quartzose sand is used, mixed with such other sub- 

 stances as carbonate of soda, slaked lime, manganese 

 peroxide, and "cullet" in definite proportions. When 

 these are melted and brought to the proper consist- 

 ency, the molten mass is poured at once upon the mold- 

 ing-plate, as the casting- table is called. For some of 

 the coarser kinds of plate glass, where translucency 

 rather than transparency is desired, the liquid is la- 

 dled out in large malleable iron ladles. But by this 

 process air bubbles are introduced, rendering the glass 

 unfit for polishing. 



The casting- table is a thick, cast-iron plate, over 



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