Turquoise, with its captivating blend of blue and green, holds a timeless allure in ceramics. Achieving a vibrant, consistent turquoise glaze at cone 6 requires careful consideration of the raw materials and their interactions at high temperatures. This guide delves into a cone 6 turquoise glaze recipe, exploring the nuances of achieving the desired shade and addressing common challenges.
Understanding the Chemistry of Turquoise Glazes
Before diving into a specific recipe, let's understand the fundamental chemistry behind turquoise glazes. The characteristic color arises from a combination of copper and other metallic oxides, often interacting with other elements like zinc or tin. Copper, the primary colorant, produces a range of colors depending on the glaze's base, firing temperature, and the presence of other oxides. A slightly alkaline glaze environment tends to enhance the blue-green hues.
A Cone 6 Turquoise Glaze Recipe
This recipe provides a solid foundation for creating a beautiful turquoise glaze. Remember that slight variations in your materials and kiln can affect the final color. Always test your glaze on test tiles before applying it to your final pieces.
Recipe (in weight percentages):
- Nepheline Syenite: 35% (Provides flux and alumina)
- Whiting: 15% (Calcium carbonate, fluxing agent)
- EPK (English China Clay): 25% (Kaolin, adds plasticity and contributes to the glaze's body)
- Copper Carbonate: 5% (Primary colorant for turquoise)
- Zinc Oxide: 10% (Influences the color and helps create a more vibrant turquoise)
- Tin Oxide: 10% (Acts as an opacifier and can influence the shade of turquoise)
Mixing Instructions:
- Weighing: Precisely weigh each ingredient using a digital scale. Accuracy is crucial in glaze formulation.
- Dry Mixing: Thoroughly mix all dry ingredients in a large bowl until evenly distributed. Avoid inhaling the dust – use a mask.
- Water Addition: Gradually add water while continuously stirring to achieve a smooth, creamy consistency, similar to heavy cream.
- Aging: Allow the glaze to age for at least a few days (or even better, a week or two) to allow the materials to fully hydrate and interact. Stir occasionally.
- Sifting: Before application, sieve the glaze through a fine mesh sieve to remove any lumps or un-dissolved particles.
Troubleshooting Common Issues
My Turquoise Glaze Turned Out Too Green:
This often occurs when the copper concentration is too high relative to the other elements, or the firing atmosphere wasn't sufficiently oxidizing. Try reducing the copper carbonate slightly and ensuring your kiln has good airflow during firing.
My Turquoise Glaze is Too Dull or Muddy:
Insufficient zinc oxide can lead to a duller color. Increasing the zinc oxide percentage can help brighten the turquoise. Insufficient tin oxide can also result in less vibrancy and opacity.
My Glaze Crazed:
Crazing occurs when the glaze expands or contracts at a different rate than the clay body during cooling. This is often caused by an imbalance in the glaze recipe. Consider adjusting the flux levels in your recipe or testing with a different clay body.
How do I adjust the intensity of the turquoise color?
The intensity of the turquoise is primarily controlled by the amount of copper carbonate and the interaction with zinc and tin oxides. Increasing copper carbonate will generally make the color more intense, but be cautious not to overdo it as this can lead to a shift towards a more green or even brownish tone. Experimenting with small variations in the percentage of copper, zinc, and tin will allow you to fine-tune the color to your preference.
What other materials can I use to create a turquoise glaze?
While copper is essential for a turquoise glaze, other materials can subtly influence the hue. For example, cobalt oxide can be added in very small quantities to deepen the blue tones, while chrome oxide can provide slightly different green undertones. However, it's advisable to experiment with these additions cautiously, as they can drastically change the final outcome.
How important is the firing temperature for a turquoise glaze?
Firing temperature is critical. Cone 6 is a common temperature for this color, but variations can significantly alter the final hue and properties. Higher temperatures tend to deepen the color and can also affect the glaze's glossiness and durability. Always test your glaze at the exact cone you intend to fire.
This recipe is a starting point. Experimentation is key to perfecting your own unique turquoise glaze. Keep detailed notes on your variations to track your progress and learn what works best in your specific environment. Remember to always prioritize safety when handling glaze materials – wear a mask and gloves, and work in a well-ventilated area.
