What happens if you fire glaze too low?

Firing ceramics involves carefully controlling temperature to achieve the desired glaze effects and overall appearance of your pottery. However, firing glaze at a temperature lower than recommended can lead to various issues that affect the quality and functionality of your ceramic pieces. Let’s explore what can happen if you fire glaze too low and the potential consequences of this firing error.

Incomplete Glaze Fusion

Glazes are composed of minerals that melt and fuse together at specific temperatures, forming a glassy surface on the pottery. Firing glaze too low can result in incomplete fusion, leaving the glaze underdeveloped, rough, or matte in appearance. The glaze may lack the desired shine, smoothness, and depth of color.

Glaze Defects

Low-temperature firing can lead to glaze defects and undesirable effects:

  • Crawling: Glaze may pull away from the clay surface, leaving bare spots or uneven coverage.
  • Pinholing: Small holes or bubbles can form on the glaze surface due to incomplete melting.
  • Poor Adhesion: Glaze may not adhere properly to the pottery, leading to flaking or chipping.

Weak and Porous Surface

Underfired glaze can result in a weak and porous surface that is more susceptible to damage, staining, and moisture absorption. This compromises the functionality and longevity of your pottery.


To avoid firing glaze too low:

  • Follow recommended firing schedules and temperature ranges for your specific glazes.
  • Use accurate temperature-measuring tools, such as pyrometers, to monitor your kiln’s temperature.
  • Test your glazes on sample tiles to determine the optimal firing temperature for desired effects.


Firing glaze at the correct temperature is essential to achieve the desired visual and functional qualities of your ceramics. Underfiring glaze can result in incomplete fusion, glaze defects, and a compromised surface. By understanding the importance of proper firing temperatures and diligently following recommended guidelines, you can create beautiful and durable pottery that reflects your artistic vision and skill.

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