Like anything that’s been around for thousands of years, the combination of science and art that is pottery has built up an enormous amount of folklore and superstitions. Jeff Zamek separates fact from fiction.
Since pottery is an endeavor that involves many steps—any of which can cause total failure—potters often misguidedly cling to a set method or technique that they think will provide a guaranteed result.
The making of ceramic objects is, at best, part science and part intuitive art. In the past, the basic science of pottery production was somewhat hit or miss. Without an extensive understanding of the underlying theories concerning ceramic materials, potters were often left with myths and inaccurate information on forming techniques, glaze formulas and firing processes.
When creating a stoneware clay body formula, one of the most important characteristics is plasticity. The unique attributes displayed by clay/water structures contribute to the plastic qualities of moist clay.
A "perfect clay body" is a subjective term, but the chances of achieving this goal increase when the appropriate ratio of clays, fluxes and fillers are used. When designing a clay body, factors such as the forming method, dry shrinkage, firing temperature, kiln atmosphere, glaze interaction, fired color, fired shrinkage, absorption and raw material availability should all be considered.
Stoneware clay is a widely used generic term for clay bodies fired between cone 6 (c/6, 2,232°F) and cone 9 (c/9, 2,300°F) that create a dense, hard, vitreous, functional piece of pottery or sculpture. Stoneware clay body formulas can contain just a few raw materials or an amalgam of several different clays, feldspar, flint, talc and grog.
With a move toward leaner, more efficient manufacturing processes, the basics of glaze formulation and application should not be overlooked.
March 1, 2005
Over the past decade, and especially within the last several years, many manufacturers of tile, dinnerware and sanitaryware have begun embracing leaner, more efficient production processes in an effort to remain competitive. As part of these initiatives, some companies have installed new glazing equipment, modified existing kilns or installed new kilns to optimize energy efficiency, developed new glaze and body formulations, investigated and/or implemented new glaze application processes, developed specially treated glaze materials, or combined different application processes (such as dry/wet) to produce new effects. While these are all important steps, the basics of glaze formulation and application should not be overlooked.
While specific technical problems are often the most visible sign of an impediment in the production cycle of forming, glazing and firing functional pottery, such problems sometimes indicate a lack of planning in other less visible, yet highly crucial areas of the business. If these problems are not detected and corrected early, they can sink the entire company.
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