Skip to content 
Pottery making is a rewarding craft, but it comes with its own set of challenges. One common issue that potters often face is the appearance of S-cracks in their wheel thrown pieces. These cracks can be frustrating, as they can damage and weaken your beautiful creations. Understanding how to deal with S-cracks can save your pieces and improve your pottery making skills.
S-cracks get their name from their shape, which resembles the letter “S”. They usually appear at the base of wheel thrown pieces and can occur either during the drying process or even after the first firing. Knowing what to look for and how to address these cracks is important for any potter.
In this article, we will explore practical ways to identify S-cracks, understand their causes, and implement preventive measures. Additionally, we will cover techniques to repair S-cracks, ensuring that your pottery making pieces stay intact and beautiful. By following these tips, you can minimise the occurrence of S-cracks and produce durable, high-quality artwork. Let’s dive into the world of S-cracks and learn how to handle them effectively.
Identifying S-Cracks in Wheel Thrown Pottery Pieces
Identifying S-cracks in your wheel thrown pottery pieces early on is crucial. These cracks are typically found at the base of the piece and often resemble the shape of the letter “S”. Knowing what to look for can help you address the issue before it worsens.
To spot S-cracks, carefully inspect the bottom of your pottery pieces during the drying process. Look for hairline fractures or splits that may start small but can grow over time. These cracks often begin in the centre of the base and extend outward in an “S” pattern.
S-cracks can also become visible after the initial bisque firing. When inspecting your piece, pay close attention to the base and any areas that seem uneven or rough. Early detection allows you to take corrective actions before the final glazing and firing steps.
Common Causes of S-Cracks in Pottery Making
Understanding the common causes of S-cracks can help you prevent them. Several factors contribute to the formation of these cracks, especially during the wheel throwing and drying stages.
1. Uneven Compression
One major cause is uneven compression of the clay during the wheel throwing process. If the base is not properly compressed, it can lead to weak spots, making it prone to cracking.
2. Drying Too Quickly
Rapid drying is another culprit. If your pieces dry too fast, the clay can shrink inconsistently, creating stress points that result in cracks. This often happens when pieces are left in direct sunlight or windy conditions.
3. Thickness Variability
Having varying thicknesses in your piece can also cause S-cracks. Thicker areas dry slower than thinner areas, leading to uneven shrinkage and, consequently, cracking.
Recognising these common causes allows you to take preventive measures, ensuring your wheel thrown pottery pieces remain intact and beautiful.
Preventative Measures to Avoid S-Cracks
Preventing S-cracks in your wheel thrown pottery pieces requires careful attention to detail and following best practices. By adopting a few key measures, you can minimise the risk of these cracks occurring.
1. Proper Compression
Ensure even compression of the clay’s base during wheel throwing. Use your finger or a wooden rib to press down at the centre of the base while throwing. This helps eliminate weak spots and ensures a uniform structure.
2. Controlled Drying
Allow your pieces to dry slowly and evenly. Cover them with plastic or place them in a damp box to control the drying process. Avoid exposing them to direct sunlight or windy conditions, which can cause rapid and uneven drying.
3. Uniform Thickness
Maintain a consistent thickness throughout your piece. Avoid making the base too thick compared to the walls. If needed, trim the base to create a more uniform thickness, which helps even with drying and reduces the risk of cracks.
4. Wedge the Clay Properly
Make sure to wedge your clay thoroughly before throwing it. This process removes air bubbles and aligns the clay particles, reducing the risk of cracks during drying and firing.
5. Use of Slip and Scoring
When attaching parts, use slip and scoring techniques to ensure they bond well. This prevents joins from separating and causing cracks.
Repairing S-Cracks During and After Pottery Making
Sometimes, despite your best efforts, S-cracks can still appear. Knowing how to repair them can save your piece and make it usable again.
During Pottery Making
1. Slip and Score: If you notice a crack forming during the throwing process, stop and repair it immediately. Score the cracked area lightly with a needle tool, then apply slip and smooth it out with your finger or a small tool.
2. Add Clay: For larger cracks, add a small amount of soft clay into the crack and blend it into the surrounding area. Compress the clay to ensure it bonds well and smooth out any excess.
After Bisque Firing
1. Epoxy Method: For cracks that become visible after bisque firing, use a two-part epoxy resin. Mix the resin according to the instructions and apply it to the crack. Allow it to dry completely before sanding it smooth.
2. Underglaze and Firing: Another method is to fill the crack with underglaze or a clay slip that matches your piece’s colour. Allow it to dry, and then refire the piece. This can seal the crack and make it less visible.
Post-Glaze Firing
1. Surface Repairs: If a crack appears post-glaze firing, you can use a ceramic filler or repair kit designed for glazed ceramics. Apply according to the instructions and let it cure fully before using the piece.
Conclusion
Dealing with S-cracks in wheel thrown pottery making pieces may seem daunting, but with the right knowledge and techniques, you can manage and even prevent them. By understanding how to identify S-cracks and their common causes, you set the foundation for addressing these challenges. Implementing preventative measures and knowing how to repair cracks can save your work and improve the overall quality of your pottery making.
At The Potters Shed, we are passionate about helping you perfect your craft. Our studio offers pottery classes where you can learn more about these techniques and refine your skills. Join us at The Potters Shed and take your pottery making to the next level. Register for our Adelaide pottery classes today and discover the joy of creating one-of-a-kind pieces.
