Glaze Course - Lesson Summaries
Firing Glazes
Lesson Number 21
The ultimate and defining stage in the process of creating a ceramic object is the firing. For most studio potters it is in the final glaze (glost) firing that the clay body is melted to the required degree of vitrification and the glaze is melted and fused to the surface of the clay.

To some extent the magical changes that take place in a glaze firing are a mystery to many. From a chemical point of view the processes are so complex that they are not fully understood by scientists least of all potters.

There are however some fundamental principles of firing an understanding of which can help us to gain some control and therefore some consistency in the quality of the fired work. Given that we have the correct mixture of materials in a recipe and have applied the mixture in a manner consistent with the requirements of a desired result, all that remains is to fire in such a way that the melting process and the cooling process will produce the kind of metamorphic change that we desire.

The factors that impact on the chemical processes that occur in firing and cooling are:

  • firing up temperature and time
  • cooling rate
  • the kiln's internal atmosphere that envelops the pots during the heating and cooling process.

Variations in these factors will result in variations in the colour, texture, fluidity etc of the glaze.

During this lesson we will discuss various methods of firing and look at specific firing schedules or cycles and the impact that atmosphere has on the chemical and physical changes that occur in the glaze during the heating and cooling process. We will also talk about kiln structure in terms of their ability to influence particularly the cooling cycle.

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