“WHITE EARTHENWARE INVESTIGATIONS. 
An extensive series of tests with bodies containing varying quan- 
titles of Cornish stone has demonstrated that the porosity of the biscuit 
burned at 1,200 degrees C. is largely dependent on the percentage of 
Cornish stone present, and that a porosity of less than 2 per cent. can 
be obtained in an eight hours’ burn at that temperature w‘th a per- 
centage of Cornish stone equal to 19 per cent. Other sets of tests have 
been carried out to show the best temperature for burning bodies, the 
effect of the presence of cobalt salts on the colour of the biscuit, and the 
effect of the various salts in maturing semi-plastic clays. 
Glazes——The glazes tried are all “raw” and “hard.” ~ 
to} 
The glazes of the type eaatt he 
"7019 f PAlLO:, 48i0,, 
and many variations of the above, by varying each and all of the con- 
stituents were fusible at and about 1,200 degrees C., but would not 
cover or mature. , 
The addition of zinc oxide greatly lowered the fusion point and 
improved their covering capacity and finish and appearance, but the 
series is not yet complete. 
Two glazes promise well, 7.¢.— 
1 yale ESS K,O 10.6 per cent. 
i .80 ZnO .5AI,O3, 3810, CaO 6.3 per cent. 
.35 CaO} ‘ ZO... 7.8 per cent. 
Al,O; ... 16.5 per cent. 
si0, 58.8 per cent. 
BA BY (0) i _ K,O 10.6 per cent. 
.30 ZnO; .4A1,03, 3.2Si0, CaO. 6.3 per cent. 
35 Gad) “nO... 7.8 per cent. 
Al,O; .... 13.1 per cent. 
SiO, ... 62.2 per cent. 
‘investigation was ordered from six to nine months ago, it has not yet 
been delivered. 
_-- Outside Work.—A fair amount of clay testing has also been done 
outside the scope of the investigation in order to assist private enter- 
prise. These number twenty-five different clays, and required the 
preparation of 100 test pieces. 
NEGF SMe 
Ff ANS 
493 
