Turquoise glazes are highly sought after for their captivating color and versatility. Achieving the perfect cone 6 turquoise, however, requires a precise recipe and understanding of glaze chemistry. This guide explores various recipes and techniques to help you create stunning turquoise glazes that fire beautifully at cone 6.
Understanding the Chemistry of Turquoise Glazes
Before diving into specific recipes, it's crucial to understand the elements that contribute to the turquoise color. Copper is the primary coloring agent responsible for the blue-green hues. The intensity and exact shade of turquoise depend on the copper carbonate (CuCO₃) content, as well as the presence of other oxides, such as tin oxide (SnO₂), which can influence the brightness and opacity. The fluxing components in the glaze also play a vital role in determining the fluidity and final appearance.
Cone 6 Turquoise Glaze Recipes: A Variety of Approaches
Several recipes can produce a desirable turquoise at cone 6. The best choice depends on the specific characteristics you're looking for – transparency, opacity, matte, or glossy finish. Here are a few examples:
Recipe 1: A Bright, Transparent Turquoise
This recipe aims for a bright, slightly transparent turquoise. Experimentation may be needed to achieve your preferred level of transparency.
- Copper Carbonate (CuCO₃): 2%
- Tin Oxide (SnO₂): 1%
- Nepheline Syenite: 28%
- Whiting (CaCO₃): 20%
- EPK (Feldspar): 30%
- Ball Clay: 19%
Note: The percentages are based on the total dry weight of the glaze.
Recipe 2: A More Opaque, Richer Turquoise
This recipe adds more tin oxide for increased opacity and a richer turquoise hue.
- Copper Carbonate (CuCO₃): 3%
- Tin Oxide (SnO₂): 3%
- Nepheline Syenite: 25%
- Whiting (CaCO₃): 18%
- EPK (Feldspar): 30%
- Ball Clay: 14%
Recipe 3: A Matte Turquoise Glaze
Achieving a matte finish requires careful consideration of the glaze's composition. This recipe incorporates zinc to achieve a softer, less glossy finish.
- Copper Carbonate (CuCO₃): 2.5%
- Tin Oxide (SnO₂): 2%
- Zinc Oxide (ZnO): 5%
- Nepheline Syenite: 25%
- Whiting (CaCO₃): 15%
- EPK (Feldspar): 28%
- Ball Clay: 10%
Factors Affecting the Final Color and Appearance
Several factors beyond the recipe itself can influence the outcome:
Firing Temperature: Even slight variations in firing temperature can significantly impact the final color. Consistent firing is crucial for reliable results.
Oxidation/Reduction Firing: The firing atmosphere (oxidizing or reducing) affects copper's behavior in the glaze. Generally, oxidation firing is preferred for turquoise glazes.
Glaze Application: The thickness of glaze application will also affect the color intensity and final appearance. Multiple thin coats generally yield better results than one thick coat.
Bisque Firing: Ensure your bisque firing is consistent, as this also affects the final glaze outcome.
Troubleshooting Common Problems
- Too Dark/Too Brown: Reduce the copper carbonate content.
- Too Light/Washed Out: Increase the copper carbonate content.
- Not Enough Opacity: Increase the tin oxide content.
- Cracking: Adjust the glaze's coefficient of thermal expansion (CTE) to match your clay body.
Experimentation is Key
These recipes provide a starting point. Experimentation is essential to achieve your perfect turquoise glaze. Keep detailed records of your tests, including all ingredients, percentages, and firing conditions. This will allow you to fine-tune your recipe and create consistent results.
Remember to always prioritize safety when working with glaze materials. Wear appropriate personal protective equipment (PPE), such as a dust mask and gloves. Dispose of glaze materials responsibly according to local regulations.
