Skip to content 
Firing up the kiln is an exciting part of the pottery process, but it can also be nerve-wracking. Kiln disasters are a common worry for potters, whether you are a beginner or have been at it for years. Understanding the common mistakes and knowing how to fix them can save you a lot of trouble and frustration.
Kiln mishaps can ruin hours of work and creativity. From cracked pots to uneven glazes, these problems can be very disheartening. However, most of these issues are avoidable with the right knowledge and techniques. By learning about frequent kiln mistakes and how to fix them, you can improve your pottery results and avoid unnecessary stress.
Recognising Common Kiln Mistakes
Understanding what can go wrong during kiln firing is crucial for preventing disasters. Here are some frequent issues that can occur:
1. Overfiring:
– Overfiring happens when the kiln temperature is too high or the firing time is too long. This can cause pottery to melt, warp, or over-glaze, ruining the piece completely.
2. Underfiring:
– Underfiring occurs when the kiln temperature is too low or the firing time is too short. Pots can come out brittle, under-glazed, or with weak structural integrity.
3. Uneven Heating:
– This occurs when parts of the kiln heat differently, leading to pieces with inconsistent finishes or colours. Uneven heating can also cause cracking or incomplete firing.
4. Improper Ventilation:
– Poor ventilation can result in fumes building up and affecting both the kiln and the pottery. It may cause discolouration or blemishes on the finished pieces.
5. Kiln Shelf Issues:
– If kiln shelves are not clean or level, it can affect the pottery. Dirt or glaze left on shelves can stick to pots, and an uneven shelf can lead to slumping or leaning pieces.
Understanding these common mistakes helps potters take steps to avoid them. Each mistake can severely impact the final outcome, making it essential to know how to prevent them from happening.
Proper Loading Techniques for Even Firing
Loading a kiln correctly is key to ensuring even firing. Proper arrangement of pottery can make a big difference in your results. Here are steps and tips to follow:
Steps for Arranging Pottery Inside the Kiln:
1. Clean Kiln Shelves:
– Before loading, make sure kiln shelves are clean and free of debris. Wipe them down to prevent dirt and glaze spots from sticking to your pottery.
2. Plan Your Layout:
– Arrange your pottery to ensure good airflow. Avoid overcrowding the kiln. Leave enough space around each piece for the heat to circulate evenly.
3. Balance the Load:
– Place larger, heavier pieces at the bottom. Smaller and lighter items can go toward the top. This helps in maintaining balance and preventing tipping or leaning during firing.
4. Stagger Shelves:
– If using multiple shelves, stagger them so the heat can flow easily around all pieces. Do not stack shelves too close together, as this can block airflow.
Tips for Spacing and Balancing Pieces:
– Leave Gaps:
– Leave a small gap between each piece to avoid them touching during firing. Touching pieces can fuse together or affect each other’s surface.
– Mind the Kiln Walls:
– Keep a bit of space between the pottery and kiln walls. Direct contact with walls can result in uneven heating or scorching.
– Use Stilts and Props:
– For delicate items or those with intricate designs, use stilts or props to keep them stable and off the kiln shelf. This helps in getting a smooth and complete firing.
By following these steps and tips, you can minimise risks and achieve even firing results. Proper loading ensures that each piece is fired correctly, reducing the chances of kiln disasters.
Managing Temperature and Timing Properly
Accurate temperature control is crucial for successful kiln firing. Mismanaging temperature and timing can lead to various issues impacting your pottery. Here’s why it’s important and how to do it right:
Importance of Accurate Temperature Control:
– Prevent Overfiring:
– Overfiring can cause pottery to warp, melt, or become too brittle. It can also lead to unsightly glaze defects.
– Avoid Underfiring:
– Underfiring can result in pottery that is weak, with glazes that appear dull or incomplete.
Guidelines for Setting and Adjusting Kiln Timers:
1. Know Your Kiln:
– Read the kiln’s manual to understand its settings and capabilities.
2. Use a Pyrometer:
– A pyrometer measures the temperature inside the kiln. This helps you monitor and adjust the heat accurately.
3. Set the Right Cone:
– Use pyrometric cones to gauge the heat work in the kiln. Choose a cone that matches the clay and glaze’s firing temperature.
4. Slow and Steady Ramp-Up:
– Increase the temperature gradually to avoid thermal shock. Rapid heating can cause pieces to crack.
5. Cool Down Slowly:
– Allow the kiln to cool down gradually. Quick cooling can lead to cracks or weakened pottery.
Following these guidelines ensures that your pottery is fired evenly and reaches the desired strength and finish. Proper temperature and timing management can make a big difference in the quality of your final pieces.
Post-Firing Checks and Fixes
After firing, it’s important to check your pottery for any defects. These checks help spot problems and give you a chance to fix them. Here are some common post-firing issues and ways to address them:
Common Post-Firing Defects:
1. Cracks:
– Look for cracks that might have developed during firing. Even small cracks can weaken the piece.
2. Blistering or Bloating:
– These are signs of trapped air or gases in the clay body or glaze. They cause the surface to bubble or bloat.
3. Crazing:
– Cracks in the glaze, usually due to mismatched shrinkage rates between the glaze and clay body.
4. Discolouration:
– Uneven or unwanted colours can appear due to improper glaze application or firing temperature.
Fixes and Preventive Measures:
– For Cracks:
– Minor cracks might be fixed with glaze or clear epoxy. For severe cracks, it’s best to learn from the mistake and try again.
– For Blistering/Bloating:
– Increase the venting time during firing to allow gases to escape. Ensure the clay is well-prepared and wedged before forming.
– For Crazing:
– Adjust the glaze formula or firing schedule to better match the clay body’s properties.
– For Discolouration:
– Test glazes before applying them to important pieces. Ensure even application and proper firing temperatures.
Regular post-firing checks help you spot and fix defects early. By understanding these common issues and how to prevent them, you can improve your pottery results and reduce wasted efforts.
Conclusion
Preventing kiln disasters is key to producing beautiful and durable pottery. Recognising common kiln mistakes and using proper loading techniques are essential steps for even firing. Managing temperature and timing carefully ensures your pottery is fired to perfection. Lastly, conducting post-firing checks helps identify and fix defects before they become bigger problems.
At The Potters Shed, we are dedicated to helping potters excel. Enrol in our pottery classes in Adelaide to discover more about firing techniques and improve your craftsmanship. Visit our ceramic studio and confidently start crafting exceptional pieces today!
