Why do we fire clay twice?

Firing clay twice, known as bisque firing and glaze firing, is a crucial process in ceramics that transforms raw clay into durable and aesthetically pleasing ceramic objects. Each firing serves a specific purpose and contributes to the overall quality of the finished piece.

Bisque Firing

The first firing, known as bisque firing, is done at a lower temperature than the glaze firing. Its primary purposes are:

  • Removing Water: Bisque firing removes any remaining water from the clay, preventing steam from forming and causing the clay to explode during glaze firing.
  • Hardening Clay: Bisque firing chemically alters the clay, making it less soluble and more durable.
  • Creating Porosity: Bisque-fired clay becomes porous, allowing glazes to adhere to the surface during the glaze firing.

Glaze Firing

The second firing, glaze firing, is done at a higher temperature to vitrify the glazes and create a glassy, decorative surface. Its main purposes are:

  • Melting Glazes: Glaze firing melts the glazes, causing them to flow and fuse to the clay surface.
  • Creating Visual Effects: Glaze firing brings out the vibrant colors, textures, and visual effects of the glazes.
  • Sealing and Protecting: The glassy glaze surface seals and protects the underlying clay from moisture and wear.


Firing clay twice is a critical process in ceramics that ensures the structural integrity, aesthetic appeal, and functionality of the final ceramic piece. Each firing contributes to the transformation of raw clay into a durable and beautiful work of art.

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