Why does underglaze smell bad?

It’s not uncommon for underglaze to emit a noticeable odor, often described as “bad” or “unpleasant,” during the firing process. This odor is primarily due to the organic materials present in the underglaze composition.

Organic Components

Underglazes contain various organic materials, such as binders, solvents, and colorants, that contribute to their workability and pigmentation. During firing, these organic components can undergo chemical reactions and release volatile compounds, leading to the characteristic smell.

Firing Temperatures

The intensity of the odor can be influenced by the firing temperature. Higher temperatures may result in a more pronounced smell as the organic materials break down and vaporize.

Health Considerations

While the smell of underglaze during firing is generally not harmful, it’s recommended to ensure proper ventilation in your kiln area to minimize exposure to any fumes that may be released.


The odor produced by underglaze during firing is a natural result of chemical reactions involving organic materials. Adequate ventilation and safety precautions can help mitigate any potential concerns.

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