An exceptionally rare painting on copper—apparently the only surviving example of its kind in Venice and among the very few known on such a monumental scale anywhere—this altarpiece was likely created in the early 1590s by Carletto Caliari, the gifted son of Paolo Veronese. The painting is dedicated to Saint Didacus of Alcalá, the 15th-century Spanish Franciscan lay brother venerated in Venice as San Diego. It shows the saint kneeling in the wilderness, a vision of the Pietà appearing above him, while food miraculously materializes on the ground before him. The scene is drawn from La vita di San Diego d’Alcalà dell’Ordine di San Francesco dell’Osservanza, published in 1590, which recounts how Diego, after begging unsuccessfully for food in a nearby town, was rewarded for his faith by God, who led him to bread, fish, and a flask of wine beside a bush along the road.

Intended for the altar of the Chapel of San Diego in the church of San Giobbe, the painting links the saint’s relatively new devotion to Venice’s established tradition of family chapel patronage. The chapel was founded in 1549 by Bernardino Testa, a wealthy textile merchant from Novara who owned a large Gothic palace, with gardens and a vineyard, on the Fondamenta Savorgnan. Two years earlier, in his will of 1547, Bernardino had entrusted his wife, Camilla, with completing the chapel, arranging for his burial there, and transferring his family’s remains from San Francesco della Vigna. The chapel is first recorded in Marco Boschini’s Minere della pittura of 1664, which notes Carletto Caliari’s copper altarpiece of San Diego, painted on that support “to protect it from the Tramontana north wind.”

Whether Carletto’s altarpiece belonged to Bernardino Testa’s original foundation remains uncertain. Neither Bernardino nor any known descendant bore the saint’s name, making a direct patron-saint connection unlikely. A later insertion appears more plausible, especially since San Diego was canonized only in 1588, after which devotion to him spread rapidly and reached Venice, finding expression in churches such as San Francesco della Vigna and San Giobbe. In this context, and given San Giobbe’s refurbishment and reconsecration in 1597, Carletto’s copper altarpiece may have replaced an earlier canvas, perhaps commissioned by Bernardino but damaged by the same strong winds that Boschini later invoked. The Testa family’s ties to San Francesco della Vigna, where the cult of San Diego also took hold in the 1590s, make the appearance of his image in their chapel at San Giobbe all the more plausible.

Over time, the family chapel became associated with the Scuola e Sovvegno di San Diego, a lay confraternity devoted to the Spanish saint. Founded only in 1610, the Scuola cannot have commissioned Carletto’s painting, as the artist had already died. Nor did it immediately assume control of the chapel: documents indicate that it obtained permission to celebrate Mass at the altar only in 1714, while ownership remained with the Testa family. Only in 1764 did the confraternity record among its possessions both the stone altar (“altar di pietra viva”) and Carletto’s copper altarpiece (“pala di rame con impronta del santo [Diego]”).

This transfer of practical control seems to have followed the inheritance of the Testa estate in 1760 by the last heir, Count Bernardino Lodovico Testa di Marsciano in Rome. Distant from the Venetian context and renting out the family properties, he likely relinquished any active claim to the chapel. Meanwhile, the Scuola’s use of the space gave it new devotional prominence. The altar and Carletto’s altarpiece were enhanced with gilded frames; a wooden crucifix on a gilded pedestal was placed above the altar; sixteen paintings depicting scenes from the life of Saint Diego were added to the side walls; and two further images of the saint were installed beside the altar.

Taken together, the evidence suggests that Carletto Caliari’s copper altarpiece emerged at the intersection of family memory, Franciscan devotion, and the rapid Venetian reception of San Diego’s cult after his canonization. Although its precise patronage remains uncertain, the painting’s unusual support, monumental scale, and placement in the Testa chapel point to a highly specific response to both local conditions and new devotional demands. Over the following century and a half, as the chapel passed from private dynastic space into the orbit of the Scuola e Sovvegno di San Diego, the altarpiece became the focal point of an expanded cultic setting, transforming an inherited family chapel into one of the saint’s most distinctive devotional sites in Venice.

Given the unusual nature of its support, copper, and the significant deterioration that have affected both the ground layer and the painted surface over the past sixty years, preliminary technical analyses are required to inform the conservation methodology and guide the planning of a carefully calibrated intervention. These investigations are essential for developing an evidence-based conservation strategy capable not only of stabilizing the work and arresting further deterioration, but also of recovering its visual coherence and enhancing its accessibility for future study and public appreciation.

Carletto Calliari (1570 – 1596)
San Diego Altarpiece
early 1590s, oil on copper
210 x 125 cm

Boschini, Marco, Minere della pittura. Venice: Francesco Nicolini, 1664. p. 486

Cicogna, Emmanuele Antonio. Delle inscrizioni veneziane, 6 vols. Venice: Giuseppe Picotti Stampatore, 1853, vol. 6.2, pp. 595-598

Celestino da Montecorvino, Lodovico (Fra). La vita di San Diego d’Alcalà dell’Ordine di San Francesco dell’Osservanza. Palermo: Gio Antonio de Franceschi, 1590

Copper as Canvas: Two Centuries of Masterpiece Paintings on Copper, 1575-1775. Oxford University Press, 1998, p. 64

Crosato Larcher, Luciana. “Per Carletto Caliari.” Arte Veneta, 21 (1967): 108-124

Hill Stoner, Joseph and Rebecca Rushfiled (eds.). The Conservation of Easel Paintings. London and New York: Routledge, 2012, p. 100

Tassini, Giuseppe. “Palazzo Testa sulla Fondamenta di S. Giobbe.” Nuovo Archivio Veneto, X, 1 (1895): 170-171

Vio, Gastone. Le Scuole Piccole nella Venezia dei Dogi. Note d’archivio per la storia delle confraternite veneziane. Costabissara (VI): Angelo Cola Editore, 2004, pp. 475-476