Glazing is a magical part of the pottery process where your raw, unglazed forms come to life with color and texture. For many potters, mixing glazes can seem daunting, but by starting with a simple base glaze like Leach 4321, you can open the door to a world of possibilities. In this post, I’ll walk you through the basics of glaze mixing and how to experiment with different oxides and carbonates to create stunning results.

What is Leach 4321?

Leach 4321 is a classic base glaze recipe that many potters use for its simplicity and reliability. The name comes from its proportions:

• 40% Feldspar
• 30% Silica
• 20% Whiting (Calcium Carbonate)
• 10% Kaolin (China Clay)

This glaze is an excellent starting point for both beginners and experienced potters who want to create their own glazes. It fires to a glossy, transparent finish in reduction and oxidation firings, making it a versatile base for experimenting with different colorants.

Getting Started: Mixing Your Glaze

Before you begin, make sure you have the proper safety equipment, such as a dust mask, gloves, and safety glasses. Dry glaze materials can be hazardous when inhaled, so always work in a well-ventilated space or wear a respirator.

Materials Needed:

• Digital scale (for accuracy)
• Sieve (80 mesh is standard)
• Stirring stick or electric drill with a mixing attachment
• Buckets (labeled for glaze storage)
• A measuring cup or graduated cylinder (for adding water)

Steps:

1. Weigh your materials according to the Leach 4321 recipe. Accuracy is important for consistent results, so a digital scale is a must.
2. Add water to the bucket and then add the dry materials to the water. this helps glaze particles into the air. It’s better to add too little water at first; you can always thin the mixture later. Aim for the consistency of heavy cream.
3. Add the dry ingredients thoroughly in a bucket. Let it slake into the water with the lid on.
4. Mix & sieve the glaze to remove any lumps or unmixed particles. This step is crucial for a smooth application and even glaze results.
5. Once your base glaze is mixed, store it in a labeled bucket for easy use. Now you’re ready to experiment with colorants and modifiers!

Experimenting with Colorants: Oxides and Carbonates

Now that you have your base glaze, you can add various oxides and carbonates to create different colors and textures. These materials will react with the base glaze during the firing process to give you a wide range of results.

Here are some common colorants and the effects they produce:

• Cobalt Oxide or Carbonate = Blue
  Cobalt is one of the most reliable and vibrant colorants, producing rich blues, even in small amounts (as little as 0.5-2%).
• Copper Oxide or Carbonate = Green (in oxidation), Red (in reduction)
  Copper is highly reactive to the firing atmosphere. In an oxidation kiln, it will turn green, while in a reduction kiln, it can produce deep reds.
• Iron Oxide = Browns and Reds
  Iron is versatile, giving you a range of earthy tones. In high concentrations, it can produce a deep red or brown, while lighter applications give more subtle yellow-brown tones.
• Tin Oxide = White (opaque)
  Tin is an opacifier, creating a clean, white surface when added to glazes. It’s great for creating a solid, bright finish.
• Zirconium Silicate = White (opaque)
  Like tin, zirconium is an opacifier but is often less expensive and can be used in similar amounts (around 5-10%).
• Manganese Dioxide = Purple-Browns
  Manganese can produce a range of purples and brownish tones, often with a speckled effect.

Testing Your Glaze

When experimenting with oxides and carbonates, start with small test batches. For example, create a series of test tiles and mix in different percentages of your chosen colorant—usually anywhere from 0.5% to 10% depending on the intensity you’re after.

1. Apply the glaze to your test tiles.
2. Fire them in your kiln, taking note of the firing temperature (cone) and atmosphere (oxidation or reduction).
3. Evaluate the results and adjust your colorant percentages as needed. Keep detailed notes for future reference.

Starting with a simple base glaze like Leach 4321 opens up endless opportunities for creative exploration. By adding different oxides and carbonates, you can produce a stunning variety of colors, from vibrant blues to earthy browns. The key to success is experimentation and patience. Document your tests, embrace the surprises, and soon you’ll develop a collection of glazes that are uniquely yours.

For further reading, we have books available for purchase here.

Happy glazing!