Materials and Techniques of Della Robbia Sculpture
The Italian term terracotta (“cooked earth”) refers to objects produced by sculpting clay and then firing it in a kiln at high temperatures to harden the material. During the Renaissance, terracotta was believed to be the oldest form of sculpture, invented in the ancient world. Luca della Robbia perfected the technique of coating terracotta in durable, colorful glazes that fused with the clay below and lent the surface a particular brightness and shine. His younger contemporary Leonardo da Vinci praised these glazes, seeing the method as a way for painting to achieve the permanence of sculpture. The characteristic look of Della Robbia terracottas was described by the 19th-century writer Walter Pater: “I suppose nothing brings the real air of a Tuscan town so vividly to mind as those pieces of pale blue and white earthenware . . . like fragments of the milky sky itself, fallen into the cool streets, and breaking into the darkened churches.”
For a closer look, click the images below.
Andrea della Robbia, Madonna and Child with Cherubim, c. 1485, National Gallery of Art, Washington, Andrew W. Mellon Collection, 1937.1.122
The recipes for glazed terracotta were closely guarded workshop secrets developed over decades and used by the Della Robbia family for about a century. The first step in the process was gathering earthen clay from riverbeds. Luca set a standard by seeking out the finest quality of clay available, a light-colored, chalky variety that bound particularly well with his lead-tin glazes. He then refined the clay through cleaning, sifting, and the addition of soft river sand.
(Left) Luca della Robbia, Madonna of the Niche, c. 1445–1455, Museum of Fine Arts, Boston, Gift of Quincy Adams Shaw through Quincy Adams Shaw, Jr., and Mrs. Marian Shaw Haughton, 17.1475
(Right) Luca della Robbia, Madonna of the Niche, c. 1445–1455, The Metropolitan Museum of Art, New York, Bequest of Susan Dwight Bliss, 1966, 67.55.98. Photograph: The Metropolitan Museum of Art/Art Resource, NY
The prepared clay was mixed with water and formed by hand-modeling, pressing it into molds, or a combination of the two techniques. A mold was used to replicate this composition. The two reliefs probably emerged from the same mold but were finished slightly differently, with details refined by hand and variations in glaze colors and applied gilding. The transparency and matte surfaces of the glaze, along with the “runny” quality of the glaze in the eyes of the New York version, suggest early experimentation with the new technique.
Luca della Robbia, The Visitation, c. 1445, Church of San Giovanni Fuorcivitas, Pistoia. Photograph: Scala/Art Resource, NY
Larger sculptures in the round were made in pieces, often hollowed out, and joined together at a later stage. Production in sections facilitated the works’ transport to destinations outside Florence. This figure group for a church in Pistoia was built in four separate parts. Once the individual pieces were formed and the clay was air dried, they were fired in a kiln at approximately 1700 degrees Fahrenheit. This step was known as “bisque firing.” The process could take several days.
Andrea della Robbia, Prudence, c. 1475, The Metropolitan Museum of Art, New York, Purchase, Joseph Pulitzer Bequest, 1921, 21.116. Photograph © 2017 Museum of Fine Arts, Boston.
After bisque firing, the sculpture was coated with glazes, composed of finely ground glass, metallic compounds as colorants, and water. Della Robbia glazes contained a high proportion of tin and lead, which lent them an opaque, bright effect. The glazes were applied by brush, sometimes in a large field of a single color, sometimes in layers to achieve various tones and shades. Then the ceramic was fired a second time at a temperature of about 1650 degrees Fahrenheit to “vitrify” the glazes, or harden and fuse them with the clay below.
Giovanni della Robbia, Resurrection of Christ, c. 1520–1525, Brooklyn Museum, New York, Gift of A. Augustus Healy, 99.5
The glazes took on their colors by the addition of various metallic compounds: tin oxide for white, cobalt for bright blue, copper for green, manganese for purple, and lead and antimony for yellow. The only primary color that could not be achieved with glaze was red. Most Della Robbia sculptures were glazed in a limited palette of one to five hues. Luca’s great-nephew Giovanni, however, distinguished himself by the use of a wider range of color and detail. The expressive quality of his lunette relief of the Resurrection was intensified by glazes in a variety of realistic flesh tones and by the addition of paint and gilding after firing. This monumental work was first recorded in an outdoor setting, at the top of a portal in the garden of an Antinori villa outside Florence. The patron, shown in prayer, was a member of that Florentine patrician family. Recent conservation of the relief was supported by his descendants through Marchesi Antinori S.p.A.
Giovanni della Robbia, Pietà, c. 1510/1520, National Gallery of Art, Washington, Samuel H. Kress Collection, 1943.4.70
In Giovanni’s Pietà, the skin tones of Mary and the dead Christ are not glazed. Instead, the terracotta is left in its natural color, enhanced by paint, to suggest the color of flesh without the addition of luminous white. Giovanni’s father, Andrea, seems to have introduced this treatment, which heightened realism, in Della Robbia holy figures of the 1490s. The innovation may have been in part a response to calls for greater simplicity and austerity in religious practice during the later 15th century.