CLAY WORKING INDUSTRIES. 109 



ing. The effect of the oxydizlng and reducing atmosphere in the color 

 produced by iron has been alluded to in the general remarks on the action 

 of heat in clays. Its application to the pottery business is vital. Potters 

 all know, practically, that clear fires throughout a burn will probably pro- 

 duce clear ware and that a choked draft or smothered fire will, infallibly, 

 produce red or brown ware. Two or more of the stoneware makers are 

 using oil fires, in order to get the advantage of perfect combustion of an 

 oxydizing heat. The clear color of the ware, in their opinion, gives 

 them an advantage which offsets the increased cost for fuel. 



Oil will not be available for fuel purposes much longer, however, and 

 the problem must be attacked on other lines. The use of fire places, which 

 are, practically, gas producers, and the use of combustion chambers to 

 effect perfect combustion of the gases from the fires, or, perhaps, the 

 direct production if it produces gas in a separate plant and its use in the 

 various kilns, will be the lines along which improvement will come. 



In cases where the iron in the clay is high and the wares are always 

 an off color, and the clay is in all other respects just what is wanted, it 

 is convenient and profitable to use a slip of a pure clay, or better still a 

 white china clay. This is done in a few places in the state and outside, 

 and one of these places has a very high reputation for the beauty of its 

 wares. The slip is applied just as the black glazes are, and when the 

 ware is salt glazed the thin layer of pure clay unites with the salt fumes 

 to produce a beautiful white salt glaze better than any natural stoneware 

 clay can produce. The expense of the clay is an item which has to be 

 considered. New Jersej^ white clays suitable for th s purpose cost from 

 $6 to §15 per ton at the mines. 



After the necessary work in making and slipping the ware has been 

 done, it is ready for setting in the kiln. In most stoneware shops this 

 is in charge of the man who does the burning. Each burner prefers to 

 supervise the setting of each kiln, in order that he may be familiar with 

 its contents and every peculiarity which call for variations in his tieat- 

 ment of the kiln under fire. 



The general principles involved in setting stoneware are: 



1. To secure a steady and even draft through all parts of the kiln, 

 and allow no short cuts from the fires to the stack. 



2. Secure solidity and good equilibrium in putting the ware in 

 position. The bottom of each tier rests on "bats" of stiff clay for 

 leveling pieces and each tier must be supported from the others by 

 "chucks" of stiff clay. 



3. The black glazed ware which is to be burnt simultaneously with 

 the salt glazed ware must be protected very carefully from the salt fumes 

 which instantly will bleach the dark colors to a light yellow. 



4. The heavy and large sized wares must be collected in the centers 

 of the kiln furthest from the points of admission of the fires in order to 



