Shivering in ceramics is a glaze defect where the glaze peels or flakes off the ceramic body, often due to a mismatch in thermal expansion between the glaze and the clay. This issue can compromise the aesthetic and functional qualities of ceramic pieces, making it crucial for ceramicists to understand and prevent.
What Causes Shivering in Ceramics?
Shivering occurs when the glaze contracts more than the clay body during cooling. This mismatch in thermal expansion can cause the glaze to separate from the ceramic surface. Several factors contribute to shivering:
- Incompatible Materials: Using a glaze that has a significantly lower coefficient of expansion than the clay body can lead to shivering.
- Improper Firing: Rapid cooling or incorrect firing temperatures can exacerbate the thermal expansion mismatch.
- Glaze Thickness: A glaze layer that is too thick can increase the risk of shivering.
- Clay Body Composition: High silica content in the clay body can lead to a greater expansion mismatch with certain glazes.
How to Prevent Shivering in Ceramics
Preventing shivering requires careful attention to material selection and firing processes. Here are some strategies:
- Match Glaze and Clay Body: Ensure the thermal expansion coefficients of the glaze and clay body are compatible. This can be tested by creating test tiles.
- Adjust Firing Schedule: Use a controlled cooling schedule to minimize stress between the glaze and clay body.
- Modify Glaze Formula: Alter the glaze composition to better match the clay body’s expansion characteristics. This might involve adjusting the silica or alumina content.
- Test with Small Batches: Before applying a new glaze to a large batch, test it on a few pieces to observe any potential issues.
Examples of Shivering in Ceramics
Shivering is often seen in functional wares like mugs and plates, where the defect can lead to sharp edges. For instance, a potter might notice small flakes of glaze separating from the rim of a mug, which could pose a safety hazard.
Why is Understanding Shivering Important for Ceramicists?
Understanding shivering is essential for maintaining the quality and safety of ceramic products. Aesthetic defects can diminish the value of the ceramics, while sharp, flaked edges can be dangerous for users. By addressing the causes of shivering, ceramicists can ensure their pieces are both beautiful and functional.
People Also Ask
What is the difference between shivering and crazing?
Shivering and crazing are both glaze defects, but they occur for different reasons. Shivering is when the glaze peels off due to a lower expansion rate than the clay body. Crazing, on the other hand, is when the glaze cracks because it contracts more than the clay body during cooling.
How can I test for shivering in my ceramics?
To test for shivering, create test tiles with the glaze and clay body in question. Fire them and observe for any peeling or flaking. You can also perform a thermal shock test by heating the tile and then quickly cooling it to see if the glaze remains intact.
Can shivering be fixed once it has occurred?
Once shivering has occurred, it is challenging to fix. The best approach is prevention through careful material selection and firing techniques. If shivering is minor, sanding the edges could reduce sharpness, but this does not address the underlying issue.
What materials are prone to shivering in ceramics?
Materials with a high silica content or those with a significant difference in thermal expansion coefficients compared to the glaze are prone to shivering. It’s crucial to test and adjust materials to ensure compatibility.
Is shivering more common in certain types of ceramics?
Shivering is more common in stoneware and porcelain due to their firing characteristics and material composition. These ceramics often require precise control over glaze and body compatibility to prevent defects.
Conclusion
Shivering in ceramics is a defect that can affect both the appearance and safety of ceramic pieces. By understanding the causes and implementing preventative measures, ceramicists can reduce the risk of shivering. Ensuring compatibility between the glaze and clay body, along with appropriate firing techniques, is key to producing high-quality ceramics. For further insights into ceramic defects, consider exploring topics like crazing and thermal shock resistance.