784: NEW YOEK STATE MUSEUM 



Other refractory articles are locomotive and steamboat tile, steel 

 runners, sleeves, nozzles, crucibles, stove linings, glass pots, gas 

 retorts, tuyeres, rolling-mill tiles, hexagon stove shapes, grate backs 

 and stove linings. 



In addition to fire bricks made from clay alone, several other 

 types of refractory bricks are recognized. 



Dinas brick are made of about 91 fo silica and Sfo of some material 

 such as lime to bind the grains together. 



Silica brick is practically another name for the above mentioned. 



Ganister is a refractory silicious rock which has about enough 

 clayey matter to hold it together when wet. 



Magnesite bricks are made of magnesite, the carbonate of mag- 

 nesia. 



Manufacture of fire brick 



Fire brick are commonly made of a mixture of clays, to which is 

 added a certain percentage of ground fire brick or burned clay, 

 and sometimes sand. If the clay is in the form of shale, it is 

 commonly ground in a dry pan, and the old brick which serve as 

 grog are treated in the same machine. 



The different ingredients are often charged into a large pit, one 

 layer over another, and the whole mass thoroughly soaked with 

 water. When sufficiently soaked the mixture goes to some form 

 of pug mill, in which it becomes more thoroughly mixed. 



In some works the clay is tempered in a wet pan, which for flint 

 clays has to be of more powerful construction than for shales. 



The molding of fire brick is ordinarily done by hand in wooden 

 molds, though a minority of fire-brick manufacturers use stiff mud 

 or soft mud machines. 



The machine-made fire brick meet objectors who say that their 

 density reduces too much their resistance to alternations of tempera- 

 ture, and the lamination imparted by stiff mud machines is also 

 brought forward as an objection; but, as fire brick clays are often 

 less plastic than many used for common or front brick, the lam- 

 inations are less pronounced. 



