INGENUITY AND LUXURY 



which is suspended a heavy iron roller, so arranged 

 that it can be set at any desired distance above the 

 table-plate. When the molten glass is poured upon 

 the table, it is rolled to the proper thickness and dis- 

 tributed evenly, by passing this roller over it just as 

 a baker uses a rolling-pin for flattening his dough. 

 In this case, however, the roller is worked by machinery. 



The moment the rolling is completed, the plate is 

 transferred to the annealing-oven. From this it 

 emerges as " rough plate" ready for grinding and pol- 

 ishing. This is done by cementing the plate to a huge 

 revolving table by means of plaster of Paris, and then 

 grinding it, first with coarse emery paper, and then 

 gradually with finer powder until the surface is even 

 and smooth. The final polish is then given it, either 

 by hand or by mechanical rubbers made of felt and 

 moistened with a solution of peroxide of iron. These 

 various processes of grinding and polishing reduce 

 the original thickness of the plate by about forty 

 per cent. 



The most vital and important part of glass-making, 

 next to the actual fusing of the metals, is the annealing. 

 This is simply a process of slow cooling after the glass 

 has been molded into shape a tempering process, 

 like the tempering of steel. If allowed to cool in the 

 open air at the ordinary temperatures, the pores at 

 the surface of the glass would close more quickly than 

 those deeper in, and a brittle, fragile product would 

 result. To avoid this, ovens with gradually dimin- 

 ishing temperatures are used, the cooling or annealing 

 process sometimes occupying several weeks. 



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