CHAPTER IV. 



THE PHYSICAL PROPERTIES OF CLAY, 



CONTENTS. 



Plasticity. 

 Tensile strength. 

 Shrinkage. 



Air shrinkage. 



Fire shrinkage. 

 Fusibility. 



Temperature of fusion. 



Determination of fusibility. 



Seger cones. 



Thermoelectric pyrometer. 

 Texture. 

 Color. 

 Slaking. 

 Specific gravity. / 



Under physical properties there are included plasticity, tensile 

 strength, shrinkage, fusibility, texture, color, slaking, absorption, 

 and specific gravity. 



PLASTICITY. 



This property permits the clay to be molded into any desired 

 form when wet, which shape it retains when dry, and while many 

 theories have been advanced to explain its cause, none of them are 

 perhaps wholly satisfactory. As is well known to all, clays show 

 a wide range in their plasticity, some being but slightly plastic 

 or lean, and others highly so- or fat. Very sandy clays containing 

 but little clay substance are usually lean, and the same is true of 

 some fine-grained ones, such as many washed kaolins. 

 6 Ch G C8i) 



