What Is The Black Clay Technique?

What is Black Clay?

Black clay, also known as barro negro, is a unique type of clay found only in the village of San Bartolo Coyotepec in the state of Oaxaca, Mexico. It gets its distinctive black color and sheen from the high iron content of the clay in that region. When fired at low temperatures between 750-800°C, the iron oxidizes and turns the clay black (Wikipedia, 2022).

The clay is famous for its unique color, smooth matte surface, and ability to retain heat. These properties make it ideal for making utilitarian pottery and cookware that is both beautiful and functional. The clay can only be found in a small region around San Bartolo Coyotepec, giving the pottery a highly localized style and tradition.

Black clay has a high iron oxide content between 8-10%, which gives it the dark color when fired. It also contains quartz particles that help give the surface an unusual smooth, soft matte finish. The clay body is dense but also rather porous, which allows it to retain heat very effectively (Obakki, 2021).

When fired at the ideal low temperatures, thequartz particles vitrify and rise to the surface, giving the silky matte surface. Higher temperatures would cause over-firing and loss of the signature darkness and soft matte texture that makes the clay so unique.

History of Black Clay

The history of black clay pottery dates back thousands of years to early Mesoamerican civilizations. Archeological evidence shows black clay vessels being produced around 500 BC in the Zapotec city of Monte Albán in what is now Oaxaca, Mexico (source). The Zapotec civilization extensively used black clay for utilitarian vessels and effigy figures. Black clay continued to be widely used for pottery among indigenous groups in Oaxaca for centuries.

The isolated village of San Bartolo Coyotepec near the ancient Zapotec capital is regarded as the birthplace of modern black clay pottery (source). Pottery crafted in San Bartolo Coyotepec still uses traditional techniques dating back thousands of years. The area’s unique clay with high iron oxide content gives the pottery its distinctive black color when fired.

Making Black Clay

Black clay is made from specific ingredients that give it its dark color and unique properties. The main ingredient is an iron-rich clay or soil, which provides the black pigmentation. According to the UNESCO Intangible Cultural Heritage site, the traditional process used in Bisalhães, Portugal involves crushing locally sourced black clay with a wooden hammer, sifting it to remove debris, and kneading it with water until it reaches the desired consistency (UNESCO).

Modern recipes may also incorporate other ingredients besides the black clay, such as Portland cement, quartz, feldspar, and grog (broken pottery pieces added to improve strength). The specific ratios depend on the clay body being formulated. These additional ingredients help modify the plasticity, shrinkage, color, firing requirements, and other properties of the clay.

Once mixed, the black clay is wedged or processed using a pugmill or other equipment to achieve an even distribution of ingredients and a uniform consistency ideal for throwing on the wheel or handbuilding. Care must be taken when mixing, as overworking the clay can introduce air bubbles that weaken fired pieces.

Working with Black Clay

Working with black clay requires some special preparation and techniques. According to Sabine Schmidt Pottery, the clay needs to be properly wedged before throwing on the wheel or handbuilding.

Wedging black clay is essential to remove any air pockets that can cause cracking or exploding in the kiln. Schmidt recommends wedging the clay thoroughly in an up and down motion rather than a circular motion to align the platelets in the clay. The clay should be wedged until it is smooth, supple, and free of cracks.

When throwing on the wheel, black clay can be sticky and prone to slumping. Schmidt advises using plenty of water to lubricate the clay and prevent it from clinging to your hands. She also recommends keeping walls thinner than normal to prevent sagging.

Overall, black clay requires patience and care when working with it. But the beautiful dark results make the extra effort worthwhile for many potters and ceramic artists.

Firing Black Clay

Firing is a critical stage in black clay pottery. When black clay is fired, several key things happen to the physical material and color of the clay:

Black clay must be fired to high temperatures, usually between 2100°F and 2300°F (source). These high temps allow the black clay to vitrify and become less porous. As the clay vitrifies, it also becomes darker in color.

Special kilns like saggar, pit, raku, and wood-fired kilns can produce an all-over black or dark gray surface on pottery (source). When fired in a reducing atmosphere with limited oxygen, black clay pots will turn very dark or black. The carbon in the clay bonds with oxygen atoms, leaving a dark color.

Firing black clay at the right temperatures and in the proper kiln atmosphere is essential for achieving very dark finishes. The intense heat and reduction atmosphere are keys to producing pottery with a deep black color and surface.

Glazing Black Clay

When glazing black clay, it’s important to choose glazes that will show up well on the dark surface. Transparent glazes work best to allow the black clay color to show through while adding glossy effects. Opaque glazes in lighter colors like white, yellow, light blue and light green will also show up well on black clay.

Glazes with lots of texture and variation in color like crystalline glazes are a great choice as they provide visual interest and contrast on black clay. Bright, vivid glazes tend to pop on the dark background. Some popular glaze choices include Amaco Velvet Underglazes, Amaco Celadons, Mayco Stroke and Coats glazes, and Amaco Shinos.

When applying glazes to black clay, it’s important to apply them thickly and use layering techniques to allow colors to overlap and create depth. The black clay absorbs light, so the glazes need opaque coverage to show properly. Testing glaze samples on test tiles is key to achieving the desired effects.

Creating Functional Ware

Making bowls, mugs, plates and other functional pieces is a common and rewarding use of black clay. The rich black color and smooth matte surface creates an elegant look for dinnerware and serving pieces. Here are some tips for success when making functional ware with black clay:

For bowls, be sure to create forms with a sturdy foot to prevent tipping. Bowls with a wide, flared rim are also less prone to chipping. Use thick walls and smooth, rounded contours for good durability.

When throwing cups and mugs on the wheel, aim for a weighty, stable base. Pull nice rounded, tapered handles for comfort and visual appeal. Attach any handles or spouts firmly using scoring and slip.

For plates, shallower forms will require less clay and dry and fire more evenly. Cut flatter bottoms so plates sit level. Decorative stamped or carved textures can make simple plates more visually dynamic.

Let functional pieces dry evenly and slowly to prevent cracks and warping. Bisque fire carefully according to the clay manufacturer’s guidelines. Smooth glaze applications to the right thickness will showcase the black color. Consider subtle accents of color with colored clay or underglazes. Clear glazing inside functional ware makes it food safe.

With good technique and patience, black clay can make stunning functional pieces that will become treasured additions to any ceramic collection.

Sculptural Work in Black Clay

Black clay is a popular material for sculptors working in a figurative, abstract, or large-scale format. The dark, raw surface and ability to show fine detail make black clay an ideal medium for sculpting works that captivate the eye.

Figurative sculptors often choose black clay for its adeptness at capturing lifelike forms. The matte surface accentuates contours and shadows, bringing out a three-dimensional realism. Many figurative artists also appreciate how black clay enhances expression through subtle facial details and emotional poise in the body.

Abstract sculptors are drawn to black clay for its visual depth and intrigue. The smooth dark surface allows light to reflect uniquely off abstract shapes and lines. Large contemporary abstract pieces in black clay can have a commanding, minimalist beauty.

For large-scale sculptures, black clay is valued for its strength and plasticity while also being lightweight. Works can be monumentally scaled without becoming prohibitively heavy. The soft sheen and fluid shapes possible with black clay bring movement and grace to oversized installations.

Notable sculptors who have worked extensively in black clay include Louise Nevelson, Edgar Degas, and Camille Claudel. Their mastery of form and texture in this medium pushed the boundaries of what clay sculpture could achieve.

Notable Black Clay Artists

Black clay has been used by many renowned ceramic artists over the years. Some of the most famous black clay artists include:

Augusta Savage (1892–1962) was an influential African-American sculptor who worked primarily in clay. She was known for her portrait busts and figures depicting African-American culture and history. Savage started the Savage Studio of Arts and Crafts in Harlem in the 1930s to provide arts education for African-American artists.¹

Selma Burke (1900-1995) was a pioneer in black clay sculpture. She was the first African-American woman to design a coin for the U.S. Mint with her profile relief of President Franklin D. Roosevelt in 1945. Burke created many portraits and figures in black clay exploring African-American identity and culture.¹

Wilmer James (1917–1999) & Tony Hill collaborated on abstract ceramic sculptures in the 1960s-1970s during the Black Arts Movement. Their works fused African and Caribbean influences with modernist abstraction. They pushed the boundaries of what could be done with black clay.¹

The Appeal of Black Clay

Black clay has an undeniable aesthetic appeal. The dark, velvety surface absorbs light in a unique way, creating depth and mystery in finished wares. This is especially striking when combined with light glazes, like white or blue, which create graphic contrast on black clay’s neutral backdrop. The color also lends itself well to carving or incising designs.

In the famous pottery village of San Bartolo Coyotepec in Oaxaca, Mexico, black clay has deep cultural significance. Indigenous Zapotec potters have been working with the local black clay for over 2,500 years, passing down techniques through generations. Their distinctive barro negro pottery captures ancient motifs and shapes in an enigmatic dark material that connects them to their ancestors.

While some clays require extensive processing, black clay is accessible and easy to work with right out of the bag. It fires to a rich, saturated black at mid-range temperatures, without the need for chemical colorants. Both handbuilders and wheel throwers will appreciate black clay’s versatility. It’s an excellent choice for potters looking for drama and visual impact.