PREFACE. Modern Ceramics may be said to date from Brogniart
1770-1847. The predominance of the French chemists in the science
of pottery during the early and middle parts of last century caused
the word Ceramic to be transplanted into English and German. Seger
and his colleagues then caused potters to turn their eyes to Berlin
for a generation but there are not wanting signs that many of Seger
s conclusions are being seriously questioned by the present school
of ceramists. New vitality has sprung from the foundation of the
American and English Ceramic Societies and from the adoption of the
science as a subject for degrees in many American Universities.
That Ceramics is suitable for University study both theoretical and
practical there can be no doubt. It is the natural means of
transition from Geology to Chemistry, Mathematics, Physics, and
Engineering. No other subject unites those five sciences so
intimately. If this book should promote the secondary and higher
study of the subject in England, the writers aim will be
accomplished. He wishes to express his indebtedness to the
Transactions of the English and American Ceramic Societies. 292432
H. H. S. CERAMIC CHEMISTRY. v. CONTENTS. Page Preface ... . y
Introduction Chapter. - - - . I. Geological Origins II. Clay III.
Clay Analysis vii. - - - 1 - 12 - 17 IV. Raw Materials - 30 V.
Bodies 37 VI. Glazes 46 VII. Enamels 52 VIII. The Production of
Colour 59 IX. Firing of the Ware - X. Loss in Manufacture - - - 71
XI. Industrial Disease - - - 75 XII. Testing of Finished Ware - - -
79 XIII. Classification of Pottery XIV. Research - . ... XV.
Bibliography in English Index of Authors - 65 84 - 82 - - 85 Index
of Subjects 89 87 CERAMIC CHEMISTRY.vii. INTRODUCTION. Ceramic
chemistry is concerned chiefly with the reactions of silicates. It
is complicated by the difference in conduct between body and glaze.
In the latter, if properly matured, the chemical reaction between
the constituents has proceeded to a finish, and the melt consists
of a homogeneous mixture or solid solution of silicates and, it
majj be, borates and phosphates, and any eutectics that may be
formed. With the body, on the other hand, it is different. The
firing is only conducted to incipient vitrification, if as high as
that. The chemical reactions are not allowed to proceed to a
finish. The chemistry of pottery is therefore, as far as the body
is concerned, one of incomplete reactions. Consequently, the nature
and condition of the raw materials are of im- are irrelevant
portance in the body, while in the glaze they as long as the same
ultimate composition is preserved. CERAMIC CHAPTER I. GEOLOGICAL
ORIGINS. The composition of the earths crust has been estimated by
several observers, the latest being F. W. Clarke 1901, who based
his calculations on 830 analyses of typical samples of the primary
rocks, and found an average of Silica 59. 71 per cent. Alumina
15.41, , Ferric oxide 2 . 63 Ferrous oxide 3 .52, , Lime 4.90
Magnesia 4 . 36, , Potassium oxide 2 . 80 Sodium oxide 3 . 55, ,
Water of combination 1 .52 Titania 0.60 Phosphoric anhydride 0.22,
, 99.22 per cent. Which leaves less than 1 per cent, for all other
combinations of elements. Clarkes figures have the molecular
formula Na2O 0.173 K2O 0.090 A1O 045 SiO2 3.0 aO 0.264 I F o 8 Oo49
Ti 2 022 I MgO 0.327 P2 5 0.005 FeO 0.146 J The melting point of
such a mixture would be about 1,200 C. As the temperature ofthe
earth, according to the figure adopted by the British Association,
increases 1 C. for every 117ft. in depth, it follows that we have
at least 25 miles of solid earth beneath us. Owing, however, to the
pressure of the superincumbent strata, the melting point of the
rocks is probably raised appreciably, but the depth given indicates
a minimum limit. The specific gravity of the primary rocks of the
earths crust is 2...
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