Creating your own ceramic glazes allows for greater artistic control, cost efficiency, and unique surface finishes. Whether you’re looking to adjust an existing recipe or formulate from scratch, understanding glaze chemistry and testing is essential.
Understanding Glaze Composition
A glaze is essentially a glassy coating fused to ceramics through firing. It consists of three main components:
- Silica (SiO₂) – The primary glass former.
- Fluxes – Help lower the melting point of silica (e.g., feldspar, calcium carbonate, lithium, sodium, potassium).
- Stabilizers (Alumina, Al₂O₃, Kaolin, Bentonite) – Prevent excessive glaze flow and add durability.
Colorants (oxides and stains) and opacifiers (such as tin oxide or zirconium) are added to achieve desired visual effects.
Essential Materials for Making Glazes
- Raw Glaze Ingredients – Feldspars, kaolin, silica, calcium carbonate, metal oxides, etc.
- Glaze Calculator Software – Tools like Glazy for adjusting formulas.
- Sieves (80-120 mesh) – For refining the glaze mixture.
- Glaze Sprayer, Dipping Tongs, or Brushes – For different application techniques.
- Test Tiles – To test variations before applying to final pieces.
Formulating Your Own Glaze
1. Start with a Base Recipe
Begin with a balanced recipe or a commercial base glaze and modify components.
A common starting point for low-fire glazes is the “50:30:20 rule.” This base recipe calls for 50% flux (usually feldspar), 30% silica, and 20% kaolin. The high flux content enables the glaze to melt at lower temperatures—typically around cone 06-04—while the silica forms the glassy network that gives the glaze its strength and durability. The addition of kaolin helps stabilize the mixture and control its flow, ensuring a smooth application and consistent appearance. This simple formulation provides a reliable baseline that you can adjust by experimenting with different ratios or incorporating colorants and additional additives to achieve your desired finish.
For high-fire glazes, a common starting point is approximately a 30:40:30 ratio, where 30% flux, 40% silica, and 30% clay (often kaolin or ball clay) are combined. This formulation is designed for firing at higher temperatures (around cone 8-10) and tends to yield glazes with a rich, earthy character and a robust, vitrified surface. High-fire glaze formulations are more nuanced, so consider this 30:40:30 ratio as an initial framework that can be fine-tuned based on your specific clay body, desired aesthetic, and firing conditions.
Both base recipes serve as excellent starting points, enabling you to systematically test and adjust your formulations to create unique and custom glazes.
2. Adjust for Desired Surface Qualities
- Glossy glazes: Increase flux content.
- Matte glazes: Increase alumina or magnesium.
- Transparent glazes: Avoid excessive opacifiers.
- Opaque glazes: Add zirconium or tin oxide.
3. Experiment with Colorants
- Iron oxide → Browns, reds, yellows.
- Cobalt oxide → Deep blues.
- Copper carbonate → Greens and turquoises.
- Manganese dioxide → Purples and browns.
4. Conduct Test Firings
Always test new glazes on small tiles at different thicknesses before applying them to your work.
Where to Find Glaze Recipes
There are several resources available for finding and sharing glaze recipes:
- Glazy – A vast online database of ceramic glaze recipes with images, chemistry calculations, and firing results.
- The Ceramic School – create a free account and browse through hundreds of glazes
- Books on Ceramic Glazing – Titles like “Mastering Cone 6 Glazes” by Ron Roy & John Hesselberth, “The Potter’s Dictionary of Materials and Techniques” by Frank Hamer & Janet Hamer, and “Glazes & Glazing: Finishing Techniques” by Anderson Turner provide valuable insights into glaze formulation and application.
- Pottery Forums and Communities – Online forums such as Ceramic Arts Network or Pottery Heads on Facebook often have shared recipes.
- Workshops and Local Studios – Learning from experienced ceramists can help you refine glaze-making techniques.
Safety Considerations in Glaze Mixing
- Wear a respirator mask (at least an FFP2 mask!) when handling dry glaze materials.
- Work in a well-ventilated area.
- Avoid toxic materials (e.g., lead, barium) for functional pottery.
- Label and store glaze ingredients properly.
Conclusion
Making your own glazes is a rewarding process that enhances creativity and control over ceramic surfaces. By understanding glaze chemistry, sourcing reliable recipes, and conducting thorough testing, you can create unique and high-quality finishes for your pottery.