Ceramic Firing: A Guide
Firing
Ceramics
The complete guide: bisque firing, glaze firing, firing temperatures and techniques – everything you need to know.
The kiln determines the color, strength, and character of every ceramic piece.
Firing is one of the most crucial steps in ceramic production. It not only gives the piece strength and durability but also significantly determines the appearance and texture of the finished product. Firing techniques and temperatures vary depending on the type of ceramic and the desired results.
In this comprehensive guide, you will learn everything about the firing process – from the two main types of firing to the correct temperature selection and special techniques such as reduction and oxidation firing. At Töpferkunst, we work with the highest precision to ensure that our dinnerware is both functional and aesthetically pleasing.
"The kiln is the final master. It decides what becomes of clay – craft or scrap."
What are bisque firing and glaze firing – and how do they differ?
Every ceramic piece undergoes two separate firing processes: bisque firing for initial hardening and glaze firing for final refinement.
Bisque Firing
Bisque firing is the first firing a ceramic piece undergoes. It occurs at a temperature of approximately 600 to 950 °C and serves to harden the piece, giving it a stable form. Bisque firing removes excess moisture from the clay – the piece becomes stable but remains porous. This porosity is important for the glaze to adhere well in the next step.
Temperature control is crucial. If the temperature is too high or the piece cools too quickly, cracks can form. Bisque firing should be done slowly and in a controlled manner – never rushed.
Glaze Firing
Glaze firing is the second firing process, where the applied glaze melts at temperatures between 950 and 1,400 °C, forming a durable surface. Glaze firing gives the ceramic its color, its glossy or matte surface, and makes it waterproof and more resistant to wear.
Successful glaze firing depends on the correct selection and application of the glaze. Depending on the glaze and firing technique, different surface textures emerge – matte, glossy, or speckled. This second firing determines the final appearance of the piece.
After bisque firing: stable, porous, and ready for glazing.
At what temperature are ceramics fired – and which kiln is the right one?
The firing temperature depends directly on the clay material. Incorrect temperatures lead to deformation, unmelted glaze, or cracks – precise work is therefore essential.
- Earthenware: 1,000 to 1,200 °C – lower temperatures, porous body, must be glazed to be waterproof.
- Stoneware: 1,200 to 1,400 °C – dense, hard material, naturally impermeable to water, ideal for everyday dinnerware.
- Porcelain: 1,200 to 1,400 °C – fine kaolin clay, very hard, translucent, sensitive to temperature changes.
- Bisque firing in general: 600 to 950 °C – applies to all clay types as the first hardening stage.
The right kiln
Various types of kilns are used for firing ceramics – depending on the desired result and technique:
Especially suitable for glaze firing, as electric kilns allow for precise temperature control. Typical for oxidation firing – colors become clear and vibrant. The standard for hobby and professional potteries.
The preferred choice for reduction firing. Oxygen levels can be precisely controlled, leading to unique rustic color and surface textures – especially with earth tones and warm hues.
Traditional and demanding – wood kilns produce irregular, distinctive surfaces through ash and changing firing atmospheres. Difficult to control, but aesthetically unique.
What is the difference between oxidation and reduction firing?
Oxidation and reduction firing produce fundamentally different aesthetic results – the choice of technique influences the color, texture, and character of the finished piece.
Reduction Firing
In reduction firing, oxygen is removed from the kiln, triggering a chemical reaction that affects the colors of glazes and clay. This process creates a distinctive, rustic look – earth colors and warm tones are emphasized. Reduction firing is predominantly carried out with gas kilns, as these allow for controlled oxygen levels.
Reduction firing is particularly popular in Raku ceramics: after firing, the piece is removed from the kiln and quickly placed in sawdust or newspapers to achieve dramatic color changes. The result is unique every time.
Oxidation Firing
In contrast, in oxidation firing, the kiln is supplied with sufficient oxygen. This method leads to clearer, more vibrant glaze colors and is primarily used in electric kilns. The colors are brighter, and the surface structure is more uniform. Oxidation firing is the preferred technique for precise coloring and reproducible results.
Left: Reduction firing with earth tones. Right: Oxidation firing with clear colors.
How to achieve optimal results when firing ceramics?
Precision and patience are the most important factors in firing. These proven tips help avoid common mistakes and achieve consistently good results.
- Temperature Monitoring: Invest in a high-quality thermometer and a reliable thermocouple to accurately monitor temperatures in the kiln. Small fluctuations can have a big impact on the result.
- Slow Cooling: Allow the kiln to cool slowly after glaze firing – at least 12 hours. Cooling too quickly causes cracks and thermal shock. Only open the kiln below 100 °C.
- Experiment with Firing Materials: If you want to achieve special colors or textures, you can experiment with firing materials like ash, salt, or tin oxide. These can create exciting effects on the surface.
- Perform Test Firings: Always conduct test firings before large series. This allows you to determine the optimal firing parameters for a specific clay and glaze without risking valuable pieces.
- Check Kiln Loading: Overloaded kilns lead to uneven temperature distribution. Pieces need sufficient space for heat to circulate evenly.
- Observe Raku Technique: In Raku firing, quickly place the pieces in sawdust-filled containers after firing to stop the oxidation process and achieve characteristic color changes.
At Töpferkunst, we work with the highest precision in both bisque and glaze firing. We precisely tailor the firing process to the properties of the respective clay and design – creating ceramic pieces that are convincing in everyday life and look beautiful. Discover the result in our Color Collection.
Firing ceramics is a fascinating and crucial process that gives each piece its final shape and function. The correct handling of firing temperatures, kilns, and techniques is essential for quality and durability. Whether bisque firing, glaze firing, or special techniques like reduction and oxidation firing – each step requires precision and experience. Those who delve into the subject will discover a world of creative possibilities at Töpferkunst and beyond. Browse through our collections and see for yourself what perfectly fired ceramics are all about.
Frequently Asked
Questions
The firing temperature depends on the clay material: Earthenware is fired at 1,000–1,200 °C, stoneware and porcelain at 1,200–1,400 °C. The first firing (bisque firing) takes place at 600–950 °C, the second firing (glaze firing) at 950–1,400 °C depending on the glaze type.
Bisque firing is the first firing at 600–950 °C: It hardens the clay, removes residual moisture, and makes the piece stable but still porous – so the glaze adheres. Glaze firing is the second firing at 950–1,400 °C: Here, the glaze melts, forms a waterproof surface, and determines the color, gloss, and texture of the finished piece.
In oxidation firing, the kiln is supplied with sufficient oxygen – colors become clear and vibrant, typical for electric kilns. In reduction firing, oxygen is deliberately reduced – this creates rustic earth tones and distinctive surface textures. Raku ceramics are the best-known example of reduction firing.
Rapid cooling causes thermal shock: The outer part cools faster than the core, leading to internal stresses and cracks. Especially after glaze firing, the kiln must cool slowly and in a controlled manner. As a rule of thumb: The kiln should be cooled below 100 °C before being opened.
Discover perfectly fired ceramics
The result of precise craftsmanship: Töpferkunst dinnerware that convinces in everyday life and looks beautiful.