Cone 6 ash glazes, fired in oxidation, offer a unique and rewarding experience for potters. Their beauty lies in the subtle variations and organic nature achievable through this firing process. This guide delves into the intricacies of creating stunning cone 6 ash glazes under oxidizing conditions, covering everything from material selection to troubleshooting common issues.
What are Cone 6 Ash Glazes?
Cone 6 ash glazes are a type of high-fire glaze made primarily from the ashes of wood-fired kilns or other organic materials. The ash itself provides the fluxing agents necessary for melting and creating a glass-like surface on ceramic ware. The composition of the ash varies greatly depending on the source material (e.g., hardwood, softwood, various plants), resulting in a wide range of color and surface effects. Oxidation firing, involving plentiful oxygen, further influences the final glaze appearance.
Why Choose Oxidation Firing for Ash Glazes?
Oxidation firing, with its abundant oxygen supply, allows for the full development of the glaze's color potential. In contrast to reduction firing, which can create dramatic color changes and often a more matte surface, oxidation generally leads to brighter, clearer colors and a more glassy finish in ash glazes. The specific colors achieved will largely depend on the ash composition and any added materials.
What are the Common Ingredients in Cone 6 Ash Glazes?
While the base of a cone 6 ash glaze is, of course, ash, other ingredients are often added to fine-tune the glaze's properties and aesthetics. These may include:
- Feldspar: To increase the glaze's melting point and fluidity.
- Whiting (Calcium Carbonate): To increase opacity and adjust the glaze's melting range.
- Nepheline Syenite: A versatile ingredient that acts as both a flux and a source of alumina.
- Silica (Silica Sand): To increase viscosity and adjust the glaze's melting point.
- Other Mineral Additives: Such as zinc, tin, or iron oxides, which may be added for specific color effects.
The precise ratios of these ingredients are critical and will be determined by testing and experimentation, dependent on the specific ash used.
How Do I Develop My Own Cone 6 Ash Glaze Recipe?
Developing your own cone 6 ash glaze recipe is a journey of experimentation and refinement. Begin by thoroughly testing your ash source to determine its base composition (this may involve lab analysis, though simple testing can offer valuable insights). You’ll then need to start with a base recipe, adjusting the proportions of other ingredients to achieve the desired properties. This iterative process involves creating test tiles, firing them to cone 6 in oxidation, and carefully observing the results.
What are Common Problems with Cone 6 Ash Glazes in Oxidation, and How Can I Fix Them?
Several challenges can arise when working with cone 6 ash glazes in oxidation. These include:
Crazing:
Crazing occurs when the glaze shrinks more than the clay body upon cooling, creating a network of fine cracks on the surface. This can be addressed by adjusting the glaze's coefficient of thermal expansion (CTE) to better match that of the clay body. Adding more silica can sometimes help.
Pinholing:
Pinholing appears as tiny holes on the glaze surface, often caused by trapped gases during firing. Ensure your glaze is thoroughly mixed and allow sufficient drying time for the ware before firing.
Crawling:
Crawling is characterized by the glaze receding from parts of the surface, leaving areas of bare clay. This often results from inadequate mixing, improper application, or incompatible glaze and clay body. Ensuring both are clean and free from oils or dust is vital.
Uneven Glaze Application:
Ash glazes can sometimes exhibit unevenness in their application. Achieving even coverage requires careful application techniques, such as multiple thin coats, and avoiding excessive brushing.
What are the Different Aesthetic Effects Achievable with Cone 6 Ash Glazes in Oxidation?
Cone 6 ash glazes fired in oxidation can offer a diverse palette of aesthetic effects, depending on the ash source and glaze recipe:
- Warm, earthy tones: From subtle creams to deep browns.
- Translucent or semi-opaque surfaces: Allowing the clay body color to show through.
- Textured surfaces: Depending on the ash composition and application techniques.
- Crystalline effects: Under specific conditions, certain ash glazes can develop crystalline formations within the glaze itself.
How can I refine the color of my Cone 6 Ash Glaze Fired in Oxidation?
Precise color control in ash glazes requires careful experimentation. Adding small percentages of metal oxides can subtly shift the color palette. For example, iron oxide can introduce warm browns and reds, while copper oxide can contribute greens or blues. Remember to test in small batches to gauge the impact of such additions.
This comprehensive guide provides a solid foundation for understanding and mastering cone 6 ash glazes under oxidation. Remember, the process is iterative; embrace experimentation and learn from each firing to achieve your desired results. The beauty of ash glazes lies in their inherent variability and the unique qualities each batch offers.
