A Course in Ceramic Materials for the Studio Potter
Mimi Obstler's Out of the Earth, Into the Fire studies glazes by examining the connection between the ceramic raw materials and the surface of a ceramic form. This book presents a twofold approach to the study of claybodies and glazes that is both empirical and historical in nature. It is empirical because it seeks to create and understand ceramic surfaces in terms of a hands-on experience with the primary minerals of our earth. It follows a historical approach in its focus on a single mineral as the core of the glaze or the claybody.
Since only hands-on testing produces the information needed to really understand ceramic materials, this book is one of the most valuable resources for potters who want to develop a true mastery of their materials.
The approach used in the book does not deny the validity of more technologically advanced methods. Obstler maintains that computer glaze software provides valuable information after the potter is familiar with the working properties of the ceramic materials of her or his glaze. In Out of the Earth, Into the Fire, glaze calculation techniques are viewed as useful diagnostic tools for the solution of glaze and claybody problems or substitutions, rather than as an essential means for the creation or understanding of ceramic surfaces.
There are only four chapters in the the book, but they exhaustively cover the materials you need for a good understanding of each topic. Chapter 1 discusses glaze cores such as feldspars and rocks, and also includes lithium glaze cores, volcanic ash glaze cores and rotten stone. Obstler concludes this and subsequent chapters with labs delineating specific tests you can run and what to observe. This testing is key to understanding how all these materials react when fired.
In Chapter 2, Clays and Claybodies, you'll discover the unique characteristics of different types of clays: kaolins, ball clays, stoneware, fireclays, and iron-rich clays. Obstler here maintains that if pottery is to thrive, we must understand the nature of clays, and she provides ample information. Each type of clay is discussed including the characteristics, its claybody function, and its glaze function.
Chapter 3 discusses auxiliary melter - materials added to the glaze-core to help it achieve a greater melt and fusion. There are many different kinds of melters, but at stoneware temperatures, it is the limestone or calcium-based melters that are most important for the stoneware glaze. The internal oxide structure of limestone is mostly calcium carbonate, which turns into calcium oxide during the firing process. For this reason, whiting, wollastonite, dolomite, gerstley borate and colemanite receive primary attention in this chapter.
Rounding out the critical components are the auxiliary silica and alumina minerals discussed in Chapter 4. In discussing silica, Obstler touches on the qualities it lends to a glaze: hardness, glassmaker, crystalline formation and the effect on fluidity and melt. Alumina posseses many unique properties as well and these are covered in depth.
In addition to detailed descriptions of the components of glazes and claybodies, Obstler includes scores of recipes and images of fired examples in low, mid-range and high fire work. The emphasis of Out of the Earth, Into the Fire is on what makes a glaze and how all the components work together. The book can be used as a course book and followed systematically from beginning to end, or as an invaluable reference book to explore any single element. A must have for any studio.