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Detail of Vincenzo Castellini, Virgin in Prayer, 1779. Micromosaic. 51 x 45 cm (20.1 x 17.7 in.). Courtesy of Alessandra Di Castro.

The Magic of Micromosaics: How Makers from Giacomo Raffaelli to Castellani Painted with Glass

Antiques dealer Alessandra Di Castro shares the history behind these portable treasures, which came into vogue during the Neoclassical period

While Venice is often considered the center of Italy’s glass manufactory, Rome is responsible for one of the country’s most distinguished art forms: micromosaics. Known in Italian as smalto filato, mosaico minuto, and mosaico in piccolo, this complex technique has inspired awe for centuries with its tesserae, pieces of colored glass less than one millimeter wide, laboriously assembled to create a perfectly rendered scene. “I have been fascinated by this extraordinary technique since my father gave me a micromosaic clock key for my bat mitzvah,” says dealer Alessandra Di Castro, whose family has sold antiques in Rome since 1878. “This key opened a world of fantasies and imagination.”

Micromosaics are a specialty of Di Castro whose holdings reflect the breadth of the technique, which can be applied to objects ranging from brooches to mantelpieces. The story of mosaics in Rome dates to the end of the 16th century with the decoration of St. Peter’s Basilica at the Vatican. However, the golden age of micromosaics can be traced to around 1800. As indicative of the Neoclassical period, the craze for antiquity was at its peak, thanks to archaeological discoveries and publications revering historical aesthetics. In 1737 at Villa Adriana in Tivoli, for example, Cardinal Giuseppe Furietti found a mosaic fragment reminiscent of a mosaic of doves that the Roman author and naturalist Pliny the Elder had famously described in a book. In 1752, the Cardinal published De Musivis, a highly influential tome on ancient mosaics with the first plate dedicated to “Pliny’s Doves,” which remain an iconic micromosaic motif today.


Giacomo Raffaelli, Micromosaic Depicting a Chaffinch on a Branch Protecting an Egg-Filled Nest from a Mouse Within a Rosso Antico Border, last quarter of the 18th century. 37 x 35 cm (14.6 x 13.8 in.). Courtesy of Alessandra Di Castro.


Giacomo Raffaelli, Micromosaic Depicting a Goldfinch on a Branch and a Serpent Below Within a Rosso Antico Border, last quarter of the 18th century. 37 x 35 cm (14.6 x 13.8 in.). Courtesy of Alessandra Di Castro.

“Because they were portable and durable, micromosaics were one of the most effective art forms for spreading Neoclassical subjects, which is why we find them in collections across Europe,” says Di Castro. Representative of the period and the Grand Tour sensibility, monuments from antiquity, including the pyramid of Cestius and Pantheon, were frequently pictured, along with Italian landscapes featuring volcanoes and waterfalls. Micromosaics also showcased paintings by key Baroque artists of the Roman and Bolognese Schools, such as Guido Reni and Guercino. Subjects that demonstrated craftsmen’s aptitude for reproducing unusual surfaces—a bird’s feathers or a butterfly’s wings—were especially desirable, along with fruits, vegetables, flower baskets, nymphs, satyrs, and animals, both still and mid-fight.

One of the earliest mosaic producers to note is Marcello Provenzale (1576–1639), who contributed to St. Peter’s Basilica, Villa Borghese, and other significant Roman enterprises. “Although the micromosaic as we currently understand it did not yet exist, Provenzale’s mosaics are made of smalto filato with splendid colors and extraordinary pictorial values,” says Di Castro. His masterpieces are now on display at the Galleria Borghese. Another important figure for the chromatic range of glass was Alessio Mattioli, who developed 28,500 tints during his lifetime. Mattioli was the first person to produce opaque enamels, which were necessary for imitating the pigments in Old Master paintings—he was also recognized for formulating porporino, a bright but opaque red. Between 1730 and 1760, he supplied glass pastes to the Studio Vaticano del mosaico, a school still active today.

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Vincenzo Castellini, Virgin in Prayer, 1779. Micromosaic. 51 x 45 cm (20.1 x 17.7 in.). Courtesy of Alessandra Di Castro.

The two names most closely associated with micromosaics are Cesare Aguatti and Giacomo Raffaelli (1753–1836). After Raffaelli, who came from a family of glassmakers, invented smalti filati—a system of spinning enamel rods which, once broken, allowed the creation of tesserae less than one millimeter thick and no longer than two to three millimeters—both he and Aguatti produced smalti malmischiati, that is, very thin rods of glass made of different colors, which caused the resulting tesserae to come in varying shades.

Beyond Raffaelli’s tremendous skill and artistic vision, he was a cunning entrepreneur, promoting micromosaics as a luxury industry beyond Rome. Around 1810, the Napoleonic government asked the mosaicist to move to Milan to establish a mosaic school. Notoriously secretive about his technique, he won numerous commissions, including one by Napoleon I to reproduce Leonardo da Vinci’s Last Supper. The mosaic can be seen in Vienna’s Minoritenkirche. Micromosaics were often a family business. Michelangelo (1787–1867) and Gioacchino Barberi (1783–1857), for instance, were prominent in producing both small and large-scale objects during the first half of the 19th century. Michelangelo extensively documented the works he made, and he was known for his tabletops, as well as scenes of dusk and nighttime. Gioacchino’s novel contribution was using colored mosaics on a black glass ground. Having worked for Russian Tsars, the Barberis created several works now held by the State Hermitage Museum in St. Petersburg.

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Gioacchino Barberi, Black Glass Paste Box with a Micromosaic Depicting Saint Benedict, c. 1815-20. 2.5 x 8 x 5 cm (0.98 x 3.1 x 1.96 in.). Courtesy of Alessandra Di Castro.

In the 19th century, three generations of the Roman Castellani family inspired a revival of Italian archaeological jewelry, including an interpretation of micromosaics (led by the firm’s chief micromosaic specialist Luigi Podio), which utilized gold rods in the tesserae. While clientele was as esteemed as Queen Margherita of Savoy, the house additionally produced objects, such as hair pins and combs, for public consumption. “When wearing micromosaics as a piece of jewelry, at the same time, you are wearing a piece of art,” says Di Castro, clad in micromosaic rings herself.

For micromosaic masters, Di Castro argues the genius is in their designs’ deception: “It’s like Impressionism: from a distance you see the complete subject, and it appears like a painting on canvas. It’s only when you get close that you see the small tesserae. The more the technique imitates the brushstroke, the more the effect is achieved.”

Exhibitor: Alessandra Di Castro | Rome
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