A PRELIMINARY REPORT ON CLAYS OV 'LORIDA 101

placed on a screen having four meshes to the inch and carefully immersed in water. The time required for the clay to disintegrate and fall through the screen is noted.
 The plasticity of certain clays is increased by weathering which thus facilitates tempering. The slaking test indicates the weathering quality of a raw clay and may be employed to ascertain whether or not weathering would facilitate handling. Also a clay which slakes readily is more easily washed than one requiring a long time for slaking.
 In the case of high-grade clays a mixture of 50 per cent clay and 50 per cent potter's flint is made into test pieces and slaked. This is one indication of the bonding strength of the clay.
 In the determination of volume air-shrinkace the volume of the test piece is determined in cubic centimeters. Then it is allowed to dry at room temperature followed by a period of drying at 1100 C. until constant in weight. The volume in cubic centimeters is again determined and the loss in volume is calculated in percentage terms of the dry volume.
 The linear air shrinkage is computed by determining the reduction during drying in the length of a line of known length marked upon the test piece when freshly molded. This shrinkage is expressed in percentage terms of the original plastic length.
 The volime fire shrinkage is determined after firing at the respective temperatures. The reduction in volume after the completion of the air shrinkage is determined in cubic centimeters and calculated in percentage terms of the original dry volume.
 The linear ire shrbihjg ge;is.deteMrmined after firing at the various temperatures in t imtee ,na th. l'ieayr. air shrinkage. It is expressed in pertn 'gq te-nis hased upoi; the. ve4tjth of the mark.
 Both -t'e.1jine'ar air and fire shrinkage may s'ahte calculated from the vqlun 'i,'shrinkagi f A :1..,ij'l gflidme and lhfai: shrinkage are simply, ?o different -erthds'of e!p'resing the samr property of a clay. 'Ihe shrinkage of a clay both in drying and in firing is obviously an important factor.
 The absorption test is made to determine the amount of water a clay will absorb. The weight of the test pieces after each firing is determined, after which they are immersed in water at room temperature for twenty-four hours and weighed again. The absorption is the amount