A PRELIMINARY REPORT ON CLAYS OE ELORIEA 91 
TEXTURE 
The size of grains composing clay varies from small pebbles to ex¬ 
tremely minute particles. In fact, these finer particles are at times 
so small as to remain in suspension in water an indefinite period. The 
size of grains, or texture, has an important influence in clays on their 
plasticity, shrinkage, porosity, fusibility and strength. 
Several methods of determining the texture of clays are commonly 
followed, and these are very similar to the methods used in the me¬ 
chanical analysis of soils. 1 
SLAKING 
Some clays when immersed in water will crumble to a powder in a 
few minutes, while others will at first break up into small masses which 
subsequently crumble. This process is known as slaking, and the test is 
usually made by mixing the clay with equal parts of ground potter’s flint. 
The time necessary for a clay to slake varies from a few minutes in soft 
porous ones to several days or even weeks in others. 
A clay which slakes easily can be tempered more readily, and in 
case of a clay which must be washed, one which slakes readily is more 
rapidly disintegrated in the process. 
SHRINKAGE 
All clays exhibit a reduction in size in drying and burning which is 
termed shrinkage. The first is the air-shrinkage and the latter is the fire- 
shrinkage. Both fire- and air-shrinkage are commonly measured in two 
ways, by volume or by linear determinations. The volume (or cubic) 
shrinkage is obtained by determining the volume of the test piece when 
first molded and again after drying or burning. The linear shrinkage is 
measured directly on the ware and expressed in percentage terms of the 
original length. 
In clay containing no water the clay particles are all in contact 
with each other. There are spaces, however, left between the particles. 
When the clay is brought into contact with water, these interstitial spaces 
are filled without the clay changing form. The water necessary to fill 
these interstitial spaces is termed the pore water. If additional water is 
1 U. S. Dept, of Agriculture, Bur. of Soils. Bull. 4, p. 9, 1896. 
U. S'. Dept, of Agriculture, Bur. of Soils. Bull. 64, 1900. 
