On the Manufacture of Glass. 



115 



to the original cost of window glass. Could we substitute 

 or discover, some substance, that, together with the other 

 essential properties of clay, was not liable to fracture, it 

 would supply what is now a great desideratum. 



The various works of masonry necessary for the manufac- 

 ture of window glass, are the following. 



1. Calcining ovens for preparing the materials. 



2. A reverberatory furnace, for fusing them. 



3. A flattening oven, for flattening and annealing the glass. 



4. Drying ovens or wood kilns, for drying the wood. 



5. A tempering oven, for burning pots and clay stone 

 generally. 



In the description which follows, of the various steps 

 which the materials are made to pass through, in converting 

 them into window glass, these several structures will be 

 briefly described. 



The vitrifiabie materials and the proportions in which 

 they are used, are the following. 



Verona sand, 100. 

 Potash, 34. 



Salt, 16. 



Lime, 5. 



Houee ashes, 15. 

 Chip glass, 30. 



Sand, 

 Kelp, 

 Lime, 

 Chip glass. 

 House ashes, 



100. 



65. 



8. 



30. 



25. 



Sand, 



Sul. Potash, 

 Lime, 



House ashes, 

 Saw dust, 

 Chip glass. 



100. 

 45. 



8. 

 15. 



2. 

 30. 



Sand, 



Sul. Soda,* 

 Lime, 

 Ashes, 

 Saw dust. 

 Chip glass, 



100. 



60. 



5. 



20. 



2. 

 20. 



This mixing is the 

 one which we have 

 commonly employ- 

 ed, and on several 

 accounts it is per- 

 haps preferable. 



Sand, 100. 



Potash, 20. 



Kelp, 28. 



Lime, 5. 



House ashes, 15. 

 Chip glass, 25. 



The sand is thrown 

 five or six hours. The house ashes are subjected to the 

 same treatment. The object is the same in both — to burn 

 away the vegetable matter, drive oft' the water, and expel 

 the carbonic acid, which the materials may contain. When 

 this is accomplished, the materials are taken from the oven, 

 allowed to cool, and sifted through a mesh ^'^ of an inch in 

 diameter. 



into the calcining oven and 



ignited 



If this salt is used containing the water of crystallization, 140 parts should 



be taken 



