What happens if kiln cools too fast?

The firing process is a critical step in ceramics, involving carefully controlled heating and cooling of pottery in a kiln. However, rapid cooling, especially if the kiln cools too fast, can have significant consequences on the final outcome of your pottery. Let’s explore what happens when a kiln cools too quickly and how it can impact your ceramic creations.

Thermal Shock

Rapid cooling of pottery from high temperatures can cause thermal shock. This occurs when the outer layers of the pottery contract quickly while the inner layers remain hot, resulting in internal stress and potential cracking. Thermal shock is a common problem when kilns cool too fast, particularly if the pottery is removed from the kiln too soon after firing.

Glaze Defects

Fast cooling can also affect the appearance and quality of glazes. Sudden temperature changes can cause glazes to improperly adhere to the pottery’s surface, leading to issues like crazing (fine cracks in the glaze) or shivering (glaze pulling away from the clay). These defects not only compromise the aesthetics of the piece but can also impact its functionality and durability.

Warping and Distortion

Uneven or rapid cooling can result in uneven contraction of the clay, leading to warping, twisting, or distortion of the pottery’s shape. This is particularly problematic for functional pieces like bowls or plates, where even minor changes in shape can affect their usability and visual appeal.

Preventing Rapid Cooling

To avoid the negative effects of rapid cooling, follow these guidelines:

  • Allow the kiln to cool gradually according to recommended cooling schedules.
  • Avoid removing pottery from the kiln immediately after firing; let it cool down inside the kiln.
  • Use kiln furniture to elevate pottery and promote more even cooling.
  • Consider using a kiln vent to regulate temperature changes.


Proper cooling is a crucial part of the firing process that significantly affects the quality and durability of your ceramics. Avoiding rapid cooling helps prevent issues like thermal shock, glaze defects, and warping, ensuring that your pottery emerges from the kiln in its best possible form and stands the test of time.

Rate article
Add a comment