Understanding the Process of the Kiln – Heating and Cooling

Introduction to Kilns


Understanding the process of how a kiln heats up and cools down is essential for any pottery enthusiast or ceramic artist. Kilns are specialized ovens used for firing clay and transforming it into durable ceramic objects. In this blog, we will delve into the fascinating journey of how a kiln heats up and cools down.

Key Points

  • Heating Up:
    • Preheating: Before firing, it’s crucial to preheat the kiln to remove any residual moisture and prevent sudden temperature changes that could cause the clay to crack or explode. The preheating process typically involves gradually raising the temperature to a low level, around 200-300°C, for several hours, depending on the size and thickness of the pottery.
    • Firing: Once the preheating is complete, the kiln enters the firing stage. During this phase, the temperature is steadily increased to the desired firing temperature, which can vary depending on the type of clay and glaze being used. The firing temperature can range from as low as 600°C for a bisque firing to as high as 1300°C or more for a high-temperature firing. The kiln may take several hours or even days to reach the desired firing temperature, depending on the size and type of kiln, as well as the thickness of the pottery.
    • Temperature Soaking: After reaching the desired firing temperature, the kiln may go through a temperature soaking period, where the temperature is held at a consistent level for a specific duration to allow the clay to mature and the glazes to melt and fuse properly. This soaking period can range from several minutes to several hours, depending on the type of clay, glaze, and firing schedule being used.
  • Cooling Down:
    • Natural Cooling: Once the firing and soaking are complete, the kiln is turned off, and the cooling process begins. During the cooling down phase, the kiln’s temperature gradually decreases to room temperature. Natural cooling is the most common method for cooling a kiln, and it’s important to allow the kiln to cool down slowly to avoid thermal shock, which can cause cracks or breaks in the pottery.
    • Ventilation: As the kiln cools down, it’s crucial to provide proper ventilation to allow the moisture and gases released during the firing process to escape. This helps prevent any pressure buildup inside the kiln, which can also cause cracks or explosions in the pottery. Kilns are typically equipped with vents or flues to facilitate proper ventilation during the cooling down process.
    • Opening the Kiln: Once the kiln has cooled down to room temperature, it’s safe to open the kiln and inspect the fired pottery. It’s important to handle the pottery with care as it will still be hot, and the glazes may be fragile at this stage. If any cracks, deformities, or other issues are detected, it’s crucial to assess the cause and make adjustments for future firings.


Understanding the process of how a kiln heats up and cools down is essential for successful pottery firing. It’s important to follow proper firing schedules, temperature guidelines, and ventilation recommendations to ensure that your pottery is fired safely and achieves the desired results. Always refer to the manufacturer’s instructions and consult with experienced potters or pottery instructors for guidance.