POTTERY OB STONEWARE CLAYS. 181 



(No. 62 S.) 

 POTTERY CLAY. 



THOMAS ROLLINS, FRANKLIN CO. 



A fine-grained tough clay, which slakts very slowly 

 when thrown into water, but splits very easily along thin 

 sandy layers which occur at intervals of about every 

 half inch, a few mica scales are present, the addition of 

 20 per cent, of water gave a workable and quiet plastic 

 paste. 



The shrinkage of bricklets made from this paste was 

 10 per cent, in drying, and 4 per cent, in burning, or a 

 total of ] 4 per cent. 



The average tensile strength of air dried briquettes was 

 102 Ibs.per square inch, with a maximum of 127 lbs. per 

 square inch. 



Incipient fusion occursat 1900° F., vitrification at 2100° 

 F., and viscosity at 2300° F. The clay burns to a red- 

 gray, but has to be heated very slowly. 



The composition of the clay is as follows: 



Analysis of Pottery Clay, Thomas BoUins, FrcmUin Co. {No. 62, S.) 



Total silica 67.50 



Aumina 19.84 



Water 6.15 



Ferric oxide 6.15 



Lime -12 



Magnesia -10 



Moisture 1-50 



Total 100.97 



Free silica (sand) 43 46 



Total fluxes B.90 



Specific gravity 2.36 



(No. 55 S.) 



POTTERY CLAY (REFRACTORY.) 



J. W. WILLIAMS, PEGRAM, COLBERT CO. 



A white clay of fine grain, which slakes easily in water. 

 The addition of 26 per cent, of water gave a lean 



