Image icon  Small ceramic pot showing centimetre scale crystals within the glaze

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Description: Careful heat treatment of the glaze produces a very small number of willemite (zinc orthosilicate, Zn2SiO4) nuclei which can grow to centimetre dimensions over the course of a few hours at a suitably high temperature. Cobalt in the glaze composition segregates preferentially to the willemite crystals, colouring them blue.
Keywords: ceramic • crystalline glaze • devitrification • willemite
Categories: Science approaches > Microstructure
Materials > Ceramics & glasses > Fired clays > Porcelain
Processes > Surface treatments
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: Dr K M Knowles, Department of Materials Science and Metallurgy, University of Cambridge
DoITPoMS, University of Cambridge
Published by: DoITPoMS, University of Cambridge
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Date created: 04 November 2002
Date added: 21 August 2009
Resource ID: 1684