Fabrication and Processing of Clay Products

Birnie, III, and W. D. Kingery, Physical Ceramics—Principles for Ceramic Science and Engineering. Copyright 1997 by John Wiley Sons, New York. Reprinted by permission of John Wiley Sons, Inc.) 

As Section 13.4 noted, this class of materials includes the structural clay products and the whitewares. In addition to clay, many of these products also contain other ingredients. After being formed, pieces most often must be subjected to drying and firing operations each of the ingredients influences the changes that take place during these processes and the characteristics of the finished piece. 

The clay minerals play two very important roles in ceramic bodies. First, when water is added, they become very plastic, a condition termed hydroplasticity. This property is very important in forming operations, as discussed shortly. In addition, clay fuses or melts over a range of temperatures thus, a dense and strong ceramic piece may be produced during firing without complete melting such that the desired shape is maintained. This fusion temperature range depends on the composition of the clay. 

In addition to clay, many of these products (in particular the whitewares) also contain some nonplastic ingredients the nonclay minerals include flint, or finely ground quartz, and a flux such as feldspar. The quartz is used primarily as a filler material, being 

When mixed with clay, a flux forms a glass that has a relatively low melting point. The feldspars are some of the more common fluxing agents they are a group of aluminosilicate materials that contain K, Na, and Ca ions. 

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