POTTERY OR STONEWARE CLAYS. 179 



(No. 23 S.) 

 STONEWARE CLAY. 



HEZEKIAH WIGGINS, FAYETTE CO. 



A light gray, hard, compact clay, of moderately silic- 

 ious character and containing a few scattered mica scales. 

 It slakes very slowly to tough scaly flakes. 



In order to make a workable pasie the clay requhed 

 the addition of 34.3 per cent, of water. This paste was 

 markedly plastic. Its shrinkage in drying was 14 per 

 cent, and 8 per cent, in burning, giving a total shrink- 

 age of 22 per cent. The tenacity of the air dried mass 

 was on the agerage 232 Ibs. per square inch with a 

 maximum of 300 Ibs. per square inch; which is exceeded 

 by comparatively few clays. 



Incipient fusion occurs at 1900 F., vitrification at 2 100 

 F., and viscosity at 2300 F. The clay burns to a dense 

 red body, but requires slow drying and heating to avoid 

 cracking. 



The composition of this clay is as follows: 



Analysis of Stoneware Clay, H. Wiggins, Fayette Co. (No. 23 S.) 



I I 



Silica (total) 63.27 



Alumina 19.68 



Water 6.05 



Ferric oxide 3.52 



Lime 1.30 



Magnesia tr. 



Alkalies 1.20 



Moisture 3.75 



88.77 



i- r c silica (sand) 39.59 



Total fluxes 6.02 



Specific gravity 2.32 



The clay agrees in composition in a general way with 

 some of the stoneware clays of Missouri and Ohio, and 

 its shrinkage and tensile strength are similiar to a ston 



