CHAPTER XIL 



TERRA-COTTA MANUFACTURE AND 

 THE NEW JERSEY TERRA-COTTA 

 INDUSTRY. 



CONTENTS. 



Raw materials. 



Terra-cotta manufacture. 



New Jersey terra-cotta industry. 



The term terra cotta is applied to those clay products used for 

 structural decorative work which cannot be formed by machinery, 

 and therefore have to< be molded by hand. 



RAW MATERIALS. 



It rarely happens that one clay alone can be used for terra 

 cotta, and consequently a mixture of several clays is employed. 

 Most of the clays chosen are No. 2 fire clays, and are, therefore, 

 buff-burning, but in their other physical properties they vary 

 widely. Some are used because of their dense-burning character 

 and bonding power, others because of a low shrinkage and free- 

 dom from warping, while absence of soluble salts is an important 

 as well as desirable property in all. 



Buff-burning clays are commonly chosen, partly because they 

 burn to a hard body at the desired temperature, and there is no 

 danger of overburning. The color of the body is of no' great 

 importance, since the final color is applied superficially. Very 

 few terra-cotta manufacturers at the present day employ a low 

 grade clay. 



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