The firing process in pottery: a deep insight into the heart of ceramics

Clay firing is a crucial step in ceramic production that determines the quality, strength and final appearance of a clay piece. In this blog post, we take an in-depth look at this fascinating process that transforms clay artworks into durable ceramics.

Basics of the firing process

During firing, the shaped and dried piece of clay is exposed to extreme temperatures to bring about chemical and physical changes in the material. These changes are permanent and decisive for the strength and water resistance of the ceramic.

The stages of the firing process

Water escape: The first phase of firing takes place at around 100-200°C, where the remaining physically bound water escapes from the clay.

Chemical change: Between 350°C and 800°C, chemical bonds in the clay begin to break down. Organic materials and other impurities burn during this phase.

Sintering: From around 800°C, sintering begins, during which the clay particles start to bond and compact. This phase is decisive for the strength of the end product.

Types of kilns

Choosing the right kiln can have a significant impact on the result. Modern ceramists mainly use three types of kilns:

Electric kilns: these are popular because of their simplicity and controllability of temperature. They are ideal for consistent and predictable results.

Gas kilns: Gas kilns allow for subtle oxidation or reduction atmospheres that allow for special glaze effects and color variations.

Wood kilns: Firing with wood is a traditional method that offers unique effects created by ash and flame that are difficult to achieve in other kilns.

The firing process: step by step

biscuit firing

The first firing is known as bisque firing and is carried out at a relatively low temperature (around 800-900°C). The aim is to make the workpiece strong enough to glaze, but porous enough to absorb the glaze.

Glaze firing

After the glaze has been applied, the piece is fired a second time, this time at higher temperatures (between 1000°C and 1300°C, depending on the type of glaze). This firing chemically bonds the glaze with the body, resulting in a shiny, often colorful surface.

The challenges of firing

Firing ceramics is not without risks. Problems such as the ware bursting due to heating or cooling too quickly, glaze effects that do not meet expectations or deformation due to overloading the kiln can occur. Experience and precise knowledge of the materials and the kiln are crucial to overcoming these challenges.

Conclusion

The firing process in ceramics is both a science and an art. Every step, from the preparation of the clay to the final firing, must be carefully planned and executed to achieve the desired results. For many ceramists, it is this process, where the fire has the final say, that is one of the most exciting aspects of ceramic production. It is an area where precision and creative experimentation go hand in hand to create beautiful, lasting works of art.