CLAYS OF KEW YORK 761 



The red owes its color to the higher state of oxidation of the 

 iron; the lower percentage of lime is due probably to its having 

 been leached out of the red clay by percolating surface waters. 



Elm Point, L. I. This clay was used for a time by the l^ew 

 York architectural terra cotta co., and also for stoneware, un(ier 

 which head it is described. < 



Terra cotta manufacture 



It rarely happens that terra cotta is made from one clay, it 

 being usually found necessary to mix several different ones to get 

 the best results. In addition to this a certain amount of sand or 

 ground brick is added to prevent excessive shrinkage. 



The clay and fire brick are ground in a dry pan; and the mixing 

 is done in a pug mill. The clay is then stored in bins till used; 

 and before the clay is sent up to the molding room it is put through 

 another pugging. 



A model is first made of every object to be constructed. Tor 

 simple forms of straight outline this can be done with the aid of 

 a templet. Thus, if a cornice is to be modeled, the ground form 

 of the piece is constructed by putting together several slabs of 

 plaster of paris; over these a mass of soft plaster is poured and 

 the templet is then two. along the surface, the pattern of it being 

 the same as the profile of the cornice. In the case of complicated 

 or elaborate forms, the model has to be molded entirely or in part 

 by hand, requiring the services of a skilled modeler. When the 

 straight edge and elaborated center of a panel or similar piece 

 are desired, the latter is modeled, while the former is obtained by 

 means of a templet. 



The model completed, a mold of plaster is next made from it. 

 This is made of several parts, which are held together by an iron 

 band, tightened with a wooden wedge. In filling the mold the 

 soft, plastic clay is forced into all the corners, till it forms a layer 

 about 2 inches thick all over the interior. The mold is allowed 

 to stand for a short time, while the clay dries sufficiently to per- 

 mit the parts of the mold to be lifted off, when the edges of the 



