Clay, compositions porcelains

The chemical composition of three kinds of English tender porcelain, together with the analyses of clays and porcelain when freed from water, is shown in the following table —... 

Kaolin, China clay, terra alba, argille, porcelain clay, and white bole are the generic names used to refer to primary clays that include three distinct white minerals - kaolinite, nacrite, and dickite - all of which share a very similar composition but differ slightly in their structure. Kaolin is rarely found pure, but as a natural mixture with other varieties of clay together, the various clays make up over 95% of the total weight of the mixture, other earthy... 

The range of clay, feldspar, and quart/, as to the ratios in the mixture and as to individual composition or each (see Tables I and 2). us well as the available range of temperature of firing makes possible the production of products of a wide variety of physical structure. There has been proposed an arbitrary line of demarcation, namely that the unglazed product, such as has been described, which absorbs not more than Iff of its weight upon and after immersion in water, shall be termed porcelain, otherwise it shall he called earthenware. Such a non porous material as porcelain, which includes chinuware. is also distinctly translucent in thicknesses of a few millimeters, whereas earthenware is nontranslucent and somewhat porous. 

The Chemical Dictionary defines porcelain as "ceramic wear made largely of baked clay (kaolin) coated or glazed with a fusible substance." Kaolin is defined as "(china clay white bole argilla porcelain clay white clay). A whiteburning clay, which, due to its great purity, has a high fusion point and is the most refractory of all clays." It gives the composition as "mainly kaolinite (40% alumina, 55% silica) plus impurities and water."... 

Certain refractories like the Marquardt porcelain used for pyrometer tubes consist essentially of sillimanite and sufficient feldspar to bring about a dense structure at about cone 18. Such a mixture would consist of a calcine fired to cone 20 having the composition 71.66 per cent kaolin and 28.34 of anhydrous alumina bonded together by clay. The mixture then would be as follows ... 

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