Glaze Course - Lesson Summaries
Glaze Defects - Crazing Part 2
Lesson Number 23
In the first part of the discussion on crazing we looked at the causes of this phenomenon. We also introduced you to the concept of the coefficient of expansion (COE) for individual oxides and for a glaze.

Although the factors that impact on crazing are quite complex we can tackle the task of manipulating crazing by utilizing our knowledge of the chemistry of a glaze.

Glaze software will calculate a coefficient of expansion for a glaze which we can use to help us determine what changes might produce more or less crazing.

The systems for calculating a coefficient of expansion for a glaze are limited and far from perfect considering the complexities of the processes in the kiln. If however we are aware of these limitations and use the numbers provided wisely, this coefficient of expansion can be a very useful piece of information in controlling what can be a very frustrating problem.

By controlling some of the issues associated with crazing we can produce interesting decorative effects that can enhance our work.

In this lesson we will:

  • examine limitations associated with the use of the coefficient of expansion as a guide to controlling crazing.
  • look at practical testing techniques that will enable us to utilize C.O.E.s for glazes.
  • formulate a strategy to tackle the task of reducing crazing in glazes.

Full lessons contain content and activities not listed above. More lessons will be added to this list as they are completed.
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Contact: Lawrence Ewing - 1015 Ellis Rd, Five Rivers, RD3, Lumsden, Northern Southland,
New Zealand