The Art and Alchemy of Saggar Fired Pottery: Exploring Ferric Chloride’s Transformative Role in Modern Ceramics

The Art & Science of Atmospheric Firing

At its core, saggar firing is a method of creating a localized, miniature atmosphere around a ceramic piece within the larger kiln. The term "saggar" comes from "safeguard," as these containers were historically used to protect delicate porcelain from the harsh wood or coal ash of the kiln.

Modern alternative potters, however, have inverted this purpose. Instead of keeping things out, the saggar is used to trap things in. By placing combustible organic materials and volatile chemicals inside a sealed container with the pottery, the artist creates a unique, oxygen-starved micro-environment during the firing. As these materials heat up, they release gases, fumes, and smoke that react with the clay surface, producing a rich tapestry of colors and patterns that can never be precisely duplicated.

Ferric Chloride: The Master Colorant

While many chemicals can be used in saggar firing, Ferric Chloride (FeCl₃) is a favorite for the stunning range of warm, earthy tones it produces.

The Chemistry of Fuming

Ferric Chloride is a volatile iron salt. As the kiln heats up, the Ferric Chloride solution vaporizes, creating a dense fume rich in iron ions. These hot, gaseous ions are highly reactive and desperately seek to bond with other elements. They are drawn to the silica and alumina in the clay body of the pot, embedding themselves in the surface and creating the signature warm palette of saggar firing.

• In an oxygen-rich (oxidation) atmosphere, the iron will produce bright reds, oranges, and yellows.
• In an oxygen-starved (reduction) atmosphere, the colors can shift to deeper browns, blacks, and even subtle metallic sheens.

This dynamic interplay between the chemical fumes and the kiln atmosphere is what makes every saggar-fired piece a unique record of its journey through fire.

A Step-by-Step Guide to the Saggar Firing Process

This process is a beautiful dance between preparation and serendipity. While you can't control the final outcome, careful preparation is key to setting the stage for amazing results.

Step 1: Preparing the Vessel (The Canvas)

The surface of your pot is your canvas. A smooth, dense surface will capture the fumed patterns most vividly.

• Choose a Clay Body: A fine, light-colored stoneware or porcelain clay body is ideal as it provides a neutral background for the colors.
• Burnish, Burnish, Burnish: The single most important surface preparation is burnishing. After the pot is bone-dry, rub the surface meticulously with the back of a spoon or a smooth stone. This aligns the clay particles, creating a tight, smooth, and slightly glossy surface that will not be glazed.
• Bisque Fire: Fire the burnished pot to a low bisque temperature (around Cone 08 or 955°C / 1751°F). This makes the pot durable enough to handle but keeps it porous enough to accept the fuming.

Step 2: Preparing the Saggar (The Micro-Kiln)

You can use a traditional ceramic saggar or create a disposable one. For beginners, a simple foil saggar is an excellent and affordable option.

Step 3: Loading the Organics and Chemicals

This is where the true artistry begins. The materials you choose will define the final pattern.

• Combustibles: Sawdust, wood shavings, and straw create a reduction atmosphere as they smolder.
• Organics for Pattern: Wrap pieces in seaweed, banana peels, or strands of copper wire. Sprinkle coffee grounds or salt crystals onto the surface.
• Applying the Ferric Chloride: Wearing full PPE, you can apply the 40% Ferric Chloride solution by brushing it directly onto the pot, or by soaking materials like string or steel wool in it and wrapping them around the piece.

Step 4: The Firing

Saggar firing is a low-temperature firing process. The goal is not to mature the clay body, but to activate the chemicals and combustibles.

After the hold, turn the kiln off and allow it to cool completely and naturally. Do not open the kiln until it is cool to the touch. This slow cooling is part of the process and prevents thermal shock.

Advanced Techniques: Expanding Your Palette

Once you've mastered the basics with Ferric Chloride, you can introduce other metal salts to create a wider range of colors.

• Copper Carbonate: Produces a range of colors from subtle pinks and reds in reduction to vibrant greens in oxidation.
• Cobalt Carbonate: Yields beautiful shades of blue. Use very sparingly as it is extremely powerful.
• Steel Wool: When wrapped around a pot, plain steel wool will create rich, dark iron markings.