Firing Porphyry in the Italian Renaissance Kiln

Chapter 3 Firing Porphyry in the Italian Renaissance Kiln Zuzanna Sarnecka In the second half of the sixteenth century a Neapolitan architect and painter, Pirro Ligorio (1510–1583), wrote a recipe for painted porphyry. As he explained, ‘when we want to imitate porphyry with paint, we make a plane of purple colour or lionato rossetto, but with some darker parts, and then, using flesh colour, we cast some small dots across the surface with a brush’.1 Here Ligorio was eloquently codifying knowledge which by then was already widespread. The time of experimentation, and of the pursuit of suitable tools and methods for carving porphyry, had already passed. This chapter will focus on an earlier era, that of the mimetic venture of the Della Robbia family of artists, who strove to produce a porphyry-like material in the ceramics kiln. The Della Robbia did not merely paint the surface of their sculptures to imitate the visual properties of the rock, as described by Ligorio, but rather, by means of a laborious and quasi-magical process of firing porphyry in the kiln, they participated in a dialogue between the artificial and the natural, between representation and actual substance. Luca della Robbia’s (1399/1400–1482) experiments with tin-lead glaze, applied to the surface of biscuit-fired earthenware and refired, constituted a distinctive Italian Renaissance project, which seems to have been inspired, at least in part, by ceramics imported from Asia, North Africa and Spain.2 Luca began glazing the surfaces of his terracotta sculptures in around the mid-fifteenth century, a technical innovation which could be seen as based upon the imitation of nature. This was an argument first advanced by Giorgio Vasari (1511–1574), a sixteenth-century artist and historiographer from Arezzo in Tuscany, who claimed (1986, 32) that Luca’s product was a cheaper alternative to natural marble. Using specific examples, I will suggest that, in fact, the three generations of the Della Robbia artists conspicuously used their technique to imitate porphyry: not only to hint at the visual properties of the natural rock, but also to add spiritual importance to their work. I will discuss various factors that might have informed Luca’s interest in the artistic and spiritual properties of porphyry, and that subsequently spurred systematic imitation of the material in the medium of glazed terracotta by his nephew Andrea (1435–1525). Then I will move on to the analysis of technical aspects involved in this process of substitution. Lastly, I will comment on the wide © Zuzanna Sarnecka, 2022 | doi:10.1163/9789004515413_006 This is an open access chapter distributed under the terms of the CC BY-NC-ND 4.0 license. Bol_and_Spary_04_Sarnecka.indd 87 18 Aug 2022 3:07:24 pm 88 Sarnecka variety of compositions and artistic uses of porphyry-like glazes in the Della Robbia sculptures, assessing the effectiveness of their attempt to mimic this rare and costly natural substance with man-made materials. The characteristic visual qualities of porphyry depend on two stages of crystallisation. One takes place in the magmatic chamber, when some of the crystals, predominantly feldspar, are formed; the second occurs during volcanic eruptions, and corresponds to the rapid cooling of the lava. The name of the rock seems related to this process of formation, for the word ‘porphyry’ evokes both fire and incandescence (pur / phur), surely for the purposes of emphasis (Malgouyres 2003, 11; Del Bufalo 2012, 12). The link between heat and porphyry was explored by Dante in his Purgatorio, where he described the third step to the doors of Purgatory as made of porphyry ‘as fiery as the blood that spurts from veins’.3 The porphyry step represented the third and ultimate stage of penitence, and the material was used to capture the burning love of God and others, which motivated the sinner to renounce the earlier sinful life. Luca della Robbia read Dante’s texts, and may have been interested in this passage and the connection between porphyry and heat, since the first step, described earlier in the canto, was made of marble, pure white and so brilliant that ‘one could see one’s reflection in its surface’.4 This passage from Dante’s Purgatorio, aside from evoking the heat of seemingly burning porphyry, also reflects the link between porphyry and blood. This association may have been reinforced by the knowledge that a deep purple dye, as intense in colour as that of porphyry, could be produced from the blood of certain molluscs, now identified as Hexaplex trunculus (Minelli 1998, 70). Porphyry signified sacrificial blood in particular, meaning that the rock was associated with the Eucharist and symbolised the blood shed for the salvation of mankind, as described in Matthew 26:28: ‘This is my blood of the Covenant, which is poured out for many for the forgiveness of sins’.5 Consequently, porphyry became an important component of celebrating the liturgy in unconsecrated spaces. Only certain stones were considered appropriate for use as altar-stones: the most common choices were marble, porphyry, jasper, alabaster, onyx and serpentine (Favreau 2003, 327–352). The eleventh-century portable altarpiece commissioned by Countess Gertrude, now at the Cleveland Museum of Art, is one of the finest examples of spiritual links between porphyry and the Passion. Gertrude belonged to a noble German family with clear imperial aspirations, as can be inferred from her marriage with Count Liudolf of Brunswick, half-brother of the emperor Henry III, and from the presence of the relics of St. Adelaide, the wife of Otto I, preserved in the altar. To emphasise the connection between porphyry and Christ’s blood, on one side of Gertrude’s altarpiece there is a cross flanked by St. Constantine and his Bol_and_Spary_04_Sarnecka.indd 88 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 89 mother St. Helen. Helen, who famously discovered the relics of the True Cross, was buried in a sarcophagus carved in porphyry, and Gertrude might have selected this stone as a top for her portable altar, not only to highlight the link between the rock and Christ’s sacrifice, but also in order to establish dynastic alignment.6 Through its seemingly impressionistic arrangement of white and pinkish dots on a deep purplish background, porphyry could capture the spilled blood, as in Stefano Lunetti’s (c.1495–1564) illumination showing the Circumcision in a manuscript at the British Library.7 The porphyry decorates the pavement of the temple around the altar, on which the standing and blessing Christ Child is being circumcised. This and similar depictions might have informed a statuette of the Christ Child (c.1490–1510) from the workshop of Andrea della Robbia, in which the luminous, white figure stands majestically on a porphyry base (fig. 3.1), which perhaps evokes the blood shed during the Circumcision and foreshadows the suffering of Christ during the Flagellation and Crucifixion. In the Christian context, the rock became a powerful visualisation of Christ’s blood spilled for the salvation of mankind, and of the bloody sacrifice made by the martyrs (Filoramo 1998, 238). In Florentine art, the connection between porphyry and martyrdom was explored by the members of the Medici family. The rock was used in several monuments to highlight the links between St. Lawrence and Lorenzo il Magnifico, the de facto head of the Florentine Republic in the second half of the fifteenth century and an important patron of the arts (Butters 1996, 49–50). Porphyry was also associated with brilliance and lustre. In his Zibaldone (1457), Giovanni Rucellai (1403–1481) wrote that ‘many wonderful slabs of porphyry […] were shiny as a mirror’.8 This quality of brilliance was difficult to capture, for instance in fresco painting, as remarked by Georges Didi-Huberman, (1995, 30), in his description of the fictive marbles painted by Fra Angelico at San Marco in Florence. Oil glazes in panel paintings and enamels allowed superior effects to frescoes, in terms of the vividness of the purple colour and imitation of the rock’s brilliance, but only enamel could compete with glazed terracotta in terms of the durability of these material and visual properties (Gavel 1979, 77–78). The Della Robbia strove to ensure the high brilliance of their reliefs by increasing the quantity of the tin oxide in their glazes (c.20% versus c.7% discovered in glazes from Casteldurante).9 This formula created high tension on the surface, especially if the sculpture in its biscuit-fired state was not cleaned and dusted properly. Moreover, because of the high proportion of tin oxide used, the Della Robbia’s glazed sculptures had to be fired at a higher temperature than other glazed earthenware, because the reduced level of lead decreased the glaze’s potential for melting. Thus, including porphyry in their compositions might have been linked to the Della Robbia ambition to Bol_and_Spary_04_Sarnecka.indd 89 18 Aug 2022 3:07:24 pm 90 Sarnecka Figure 3.1 Andrea della Robbia workshop, Christ Child, c.1490–1510, glazed terracotta London, Victoria and Albert Museum (photo: Victoria and Albert Museum, London) Bol_and_Spary_04_Sarnecka.indd 90 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 91 show the brilliant surfaces characteristic of the polished rock but successfully mimicked in glazed terracotta. As one of the hardest stones known, and because of its deep purple colour, porphyry was associated with empire and rulership. Apart from imperial sarcophagi, it was also used in statues commemorating the deeds of various rulers.10 One example of this practice is the group of The four tetrarchs in Venice, which at times was believed to have apotropaic powers, because of the agency of porphyry (Tronzo 2012, 49). The skilful modelling of the figures seems miraculous, especially if we consider that the smoothing of one square meter of porphyry required 150 working hours, compared to the 5 or 6 hours required for its equivalent in Carrara marble.11 Furthermore, Vasari’s famous description of Leon Battista Alberti’s struggle to incise the patron’s name on the porphyry doorstep to the entrance of the church of Santa Maria Novella in Florence reveals that the skill and tools necessary for carving the rock were long lost by the early fifteenth century: ‘In our days, the mastery of working this kind of rock is unavailable, since our artisans have lost the skill of sharpening the iron, and thus the tools to carve the material’.12 Because of its hardness, porphyry was also employed in artists’ workshops for grinding pigments, as described in several instances by Cennino Cennini (1370–1440): ‘take a slab of pink porphyry, which is a strong and resistant stone. For there are several kinds of stones for grinding colours, like porphyry, serpentine and marble […] but porphyry is superior to them all. And if you take one of the very, very bright ones it is better, one of the ones that is not completely polished […] Then take a stone to hold in your hand, also of porphyry, flat at the bottom and cupped at the top, shaped like a bowl […] so that your hand should be able to draw and guide it here and there as it pleases’.13 It was no accident that Pier Maria Serbaldi da Pescia (c.1455–after 1522), credited with recovering the art of carving porphyry in the early sixteenth century, was a gem-cutter used to working with hard and precious materials.14 However, even after the rediscovery of suitable tools and techniques, the material’s relative hardness meant that carving and polishing large-scale porphyry figures was a long and painstaking process (Bol 2018, 223–257). The most celebrated Renaissance sculptor in porphyry, Francesco Ferrucci del Tadda, dedicated his whole career to this single material, as it took him and his sons about twelve years to carve one full-figure statue of Justice (Butters 1996, 294). In the early fifteenth century, humanists in Florence gained greater access to Ptolemy’s Geographia, thanks to a Latin translation of the Greek text by Jacopo Angeli da Scarperia (Hawkins 2003, 457–468). Luca della Robbia’s contacts with Florentine scholars meant that the processes underlying the production Bol_and_Spary_04_Sarnecka.indd 91 18 Aug 2022 3:07:24 pm 92 Sarnecka of the stone could have been familiar to the Della Robbia artists.15 Our appreciation of porphyry has changed over time, with increased awareness of its material properties and the rediscovery of the quarries from which the rock was extracted. Mons Porphyrites, modern Gebel Abu Dukhan, located in Egypt close to Hurghada, remained a mystery from Antiquity until the 1820s. The mining of porphyry was notoriously laborious. Probably because of this, its quarries were abandoned in the 5th century AD (Ward-Perkins 1971, 141–149). This meant that rocks that had already been extracted were reused over time in different contexts, and it was this recycled porphyry, taken predominantly from antique architecture, that was admired and used in Europe between the 6th and 18th centuries. During the fifteenth and early sixteenth centuries, the process of making glazed terracotta was not widely understood, and family recipes were strictly guarded. This secrecy went hand in hand with the unfamiliarity of the material properties of actual porphyry. Whilst members of the Della Robbia workshop clearly benefitted from the knowledge and practical know-how of the ceramics industry, its limited influence in the late fifteenth century on the art of maiolica might be linked to the importance placed on secrecy in the artistic world and the limited circulation of knowledge (Sarnecka 2017). The possible exchange of technical know-how between artists’ workshops, which was characteristic of Florence and Italy in general in the fifteenth century, apparently did not extend to the realm of glazed terracotta sculpture (Marini 2009, 59). As we learn from Luca’s will, drafted in 1472, he left his art to just one person, his highly-skilled nephew Andrea. Unlike Theophilus in the twelfth century or later writers such as Vannoccio Biringuccio (c.1480–c.1539) or Cipriano Piccolpasso (1524–1579), Luca did not promote openness of knowledge and the free circulation of available glazing methods. Piccolpasso, for instance, openly criticised people who shared the secrets of their arts on their deathbeds and only with their oldest sons.16 Rather, Luca followed the artisanal strategy of limiting access in order to ensure stable financial profits. The art of glazing had a monetary value: in Luca’s will, the secret is mentioned as a transmissible property after a reference to a sum of money given to the Opera del Duomo, and before the section dealing with his house.17 It was not so much the immaterial knowledge that Andrea was to inherit after Luca’s death, but rather the financial gain associated with secrecy and exclusive access to the recipe. Imitating porphyry in this medium added another layer to the perceived artistic supremacy of the Della Robbia production. It is possible that the Della Robbias’ imitation might have been informed to an extent by certain doubts about the material properties of porphyry which persisted through the fifteenth century. Ruy González de Clavijo, who travelled Bol_and_Spary_04_Sarnecka.indd 92 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 93 to Constantinople in 1406, made notes on what he believed was the way of making porphyry. In his description of the interior of Hagia Sophia, de Clavijo (1859, 37) wrote about the arches underneath a dome as being decorated by ‘four very large slabs, two on the right hand and two on the left, which are coloured with a substance made from a powder, artificially, and called porphyry’. This account is important, since it reveals the confusion between the natural rocks and manmade materials obtained artificially from coloured dust. Clavijo used the word pílfido, a variation deriving from the Greek word meaning ‘of purple colour’. This Greek word was later adopted into Italian, and was heard in this form by Pedro Tafur, who travelled to Italy.18 In 1450, Giovanni Rucellai (1960, 69, 72, 74) used the word porfido in various descriptions of interiors, such as the eight columns in the Sistine Baptistery or the pavement of the choir in the old church of San Giorgio in Venice. However, the term itself did not circulate widely in the first decade of the fifteenth century. It is therefore possible that Ruy González heard it in Constantinople, and, not being familiar with the material properties of the natural porphyry, thought that it was an artificial material. Suzanne Butters, discussing this same quote (1996, 43), has assumed that De Clavijo was looking at a fictive porphyry, rather than thinking that porphyry slabs had to be made by artificial means. To support her interpretation, Butters cites a recipe book from the late sixteenth to early seventeenth century, by which date the material properties of porphyry were widely recognised, as were the imitations of this rock in other materials such as wood or indeed glazed terracotta.19 However, in the early fifteenth century, the lack of understanding of the process of formation of porphyry, and the inaccessibility of the quarries where it was to be found, encouraged a general scholarly audience, including travellers such as De Clavijo, to question the rock’s natural character. Various observers and chroniclers suggested that porphyry was fabricated from water and purple dye. Towards the end of the fifteenth century, an anonymous Ottoman writer disputed the common belief that porphyry was a frozen, water-based dye. He noted that: […] since no person has seen the marble quarry, certain people say that the [stone] called porphyry is artificially made. They say that, during ancient times, according to the quantity of columns required, they made moulds and channelled water into them. Afterwards they added the desired colour to the water, and then they had a plant, and they also added this plant to the water and the water solidified and became marble, it is said […] Moreover, if it applied to a single colour, one might find grounds for believing it. But since there exist marbles of three or four Bol_and_Spary_04_Sarnecka.indd 93 18 Aug 2022 3:07:24 pm 94 Sarnecka colours, it is impossible to add one colour to water and obtain three or four colours and veining; reason cannot accept such a thing.20 The application onto one surface of three colours and stippling was possible, however, through the medium of glazed terracotta. The lack of understanding of the Della Robbia technique by their contemporaries only added to the material mystery of the imitation of porphyry with glazes, and contributed to the creation of the artistic myth. A similar material mythology was established in relation to bronze, as discussed by Frits Scholten (2005, 20–35), who stresses that dependence on an unknown outcome ensured the quasi-magical effect of the final artistic product. This uncertainty was linked to the difficulty of obtaining accurate temperatures in the kiln, to ensure a successful cast in the case of bronze, and in the case of glazed terracotta to ensure a lack of air bubbles and to prevent glazes from running. That spiritually engaged activities took place in the workshop on Via Guelfa can be inferred from Piccolpasso’s Three books of the potter’s art (c.1557). Piccolpasso stressed the importance of offering prayers to God for the successful firing of the clay: ‘When you have finished all this, direct your prayers to God with all your heart, thanking Him for all that you receive’.21 In a different passage, Piccolpasso encouraged further praise of God’s name: ‘Always remember to do all your activities in the name of Jesus Christ, with that in mind light the fire’.22 The document confirms that the difficult process of controlling the temperature in the kiln and the successful firing of meticulously prepared terracotta ware were placed in God’s hands, in the belief that the outcome relied on His grace. We find similar links between skill and devotion in Cennino Cennini’s account of drawing on gilded glass, when he recommends: ‘Tie a needle to a little stick as if it were a little hairbrush, and it should be really fine at the tip and, invoking God’s name, begin drawing the figure that you want to do lightly with this needle’.23 Similarly, Theophilus stressed in his treatise that all knowledge was given to men through the grace of the Holy Spirit and the sevenfold gifts. Wisdom is necessary ‘to know that all created things proceed from God, and without Him nothing is’, while the fear of the Lord ensures that ‘you remember that you can do nothing of yourself; you reflect that you have or intend nothing, unless accorded by God’.24 Both medieval and Renaissance writers on the arts clearly linked craft to piety.25 We may assume that Luca was intimately aware of, and wished to imitate in his sculpture, the material importance, spiritual significance and quasimagical properties of porphyry, not least because of his friendship with many Florentine humanists. In 1433, Luca’s close friend Niccolò Niccoli received a letter from Ambrogio Traversari, in which he discussed the beauty of a porphyry vase from Santa Maria in Porto in Ravenna. He wrote that: ‘the simpler Bol_and_Spary_04_Sarnecka.indd 94 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 95 friars think it is one of the water jars in which the Evangelist attests that water was changed into wine’. In the letter, the vase is described as: ‘made of porphyry, beautiful and sculpted (tornatile)’.26 Tornatile, derived from the Latin tornatilis, emphasises the importance of craftsmanship, as it implies that the vase was beautifully finished and worked, and that it was not just a piece of quarried porphyry, precious in itself, but was carved by the equally miraculous work of the artist who gave the material its specific form. Being both a devout man and a supreme artist, Della Robbia might have considered the spiritual significance of the miraculous transformation of matter. The first miracle performed by Christ was to change water into wine during the Wedding at Cana (John 2:1–11): through experiments with glazes, Luca could have transformed a liquid substance into something that visually resembled one of the hardest and most valuable of stones.27 The technical challenges posed by imitating the colour and texture of porphyry in other media might also have prompted Luca’s interest in the rock. In his natural history, well-known to Renaissance readers, Pliny the Elder reported (1855, book 35, chapter 31) that purpurissum belonged to the category of pigments which cannot be applied onto the fresh intonaco, and therefore could not be used in painting in the technique of buon fresco. For this reason, and because of the expensive nature of the pigment, the colour was recommended to be used very sparingly and rarely in wall painting, only in the most important commissions, and by highly-qualified workshops (Salvadori 1988, 206). Indeed, instances of fresco-painted illusionistic porphyry are relatively rare, and artists who wished to imitate this rock, such as Pietro Lorenzetti in painting the scene of the Resurrection in the Lower Church at Assisi, used the more widely available hematite, which was an iron oxide stone of a dark red hue (Malgouyres 2003, 13). Imitating porphyry on the verso of painted portraits was more common, both in Italy and in Northern Europe.28 However, even if a deep purple was used in frescoes or panel paintings to imitate porphyry, it lacked the texture of the actual stone. This was a quality that could be imitated with greater success through the use of tin glazes on the biscuit-fired surface of terracotta. The extensive use of the widely available manganese purple in the art of ceramics may have been another technical aspect that informed the imitation of porphyry in the Della Robbia workshop. As described by Cipriano Piccolpasso in his treatise on the potter’s art, manganese was to be found in abundance in different places throughout Tuscany.29 Moreover, during the fifteenth and sixteenth centuries, vividly red fired glazes were notoriously difficult to obtain. As lamented by Piccolpasso (1980, 104), red was unreliable, and he had seen the colour fired successfully only once in a workshop of Vergiliotto in Faenza, who used levigated Armenian bole (material widely used by painters Bol_and_Spary_04_Sarnecka.indd 95 18 Aug 2022 3:07:24 pm 96 Sarnecka as a preparatory layer underneath a gold leaf in paintings and polychromy). Manganese purple was the closest colour to red that one could use in decorating ceramics. The glazed terracotta relief showing the Adoration of the Magi, by an anonymous artist probably from Faenza, exhibits a variety of elements, including lips, garments and shoes, painted using manganese purple, which at times seems very close to the purplish colour used by the Della Robbia to imitate porphyry (fig. 3.2). Apart from these technical considerations that might have motivated Luca and subsequent members of his family to engage with the imitation of porphyry, there may also have been a sense of familial interest in the material. As observed by Giancarlo Gentilini (1992, 11), the family name derives from a plant called robbia, from the root of which was obtained a dye of intense red colour. In his De architectura (7, 14, 2), Vitruvius wrote of the imitation of purple colours – purpurei colores – that they could also be obtained by applying the root of this plant to clay, or by dyeing clay with hysignum. Gentilini suggests that the wealth of the Della Robbia family, from the early fourteenth century onwards, may have come from trade in this dye, which they either produced in Tuscany, or imported, principally from the Levant.30 Taking these factors into account, it should be emphasised that Luca’s sculptures were not celebrated for their mimetic qualities. In fact, he is most renowned for his unparalleled and otherworldly white surfaces on reliefs of the Virgin and Child. Early in his glazed terracotta production, Luca was urged by his patrons to imitate the actual colours of things represented using his glazes, as in the case of the second lunette for the doors to the Old Sacristy of the Florentine Duomo (Planiscig 1948, 30). In the first lunette for the Sacrestia delle Messe, showing the Resurrection of Christ (1442–1444), Luca exclusively used white glazes for all figures, foliage and other elements of the composition, set against a blue background. He made no attempt at naturalistic imitation of the visual properties of any material, including porphyry on the opened sarcophagus, as subsequently done in numerous representations of the same iconography executed by Andrea. In the Ascension lunette (1446–1451) designed for the space above the doors to the Old Sacristy, the trees and rocks are in their natural colour. This was a direct consequence of the contract, which asked Luca to take into account the true appearances of things and to try to imitate them in his work.31 What seems important is that the lack of a porphyry-like glaze on the lunette showing the Resurrection cannot be explained by technical shortcomings, nor by the restrictions of Luca’s palette, for he used purplish glazes to decorate the Peretola tabernacle, completed in 1442, before he received the commission for the first lunette (fig. 3.3).32 The colour was used to paint one putto in the centre of the architrave of the architectural frame. The manganese Bol_and_Spary_04_Sarnecka.indd 96 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 97 Figure 3.2 Anonymous Artist (Faenza?), Adoration of the Magi, c.1490, glazed terracotta London, Victoria and Albert Museum (photo: Victoria and Albert Museum, London) Bol_and_Spary_04_Sarnecka.indd 97 18 Aug 2022 3:07:24 pm 98 Sarnecka Figure 3.3 Luca della Robbia, The Peretola Tabernacle, c.1441–42, glazed terracotta, bronze, marble Peretola, Church of Santa Maria. Photo: Federica Carta Bol_and_Spary_04_Sarnecka.indd 98 18 Aug 2022 3:07:24 pm Firing Porphyry in the Italian Renaissance Kiln 99 Figure 3.4 Luca and Andrea della Robbia, Stemma of Jacopo Pazzi, c.1460–65, glazed terracotta Florence, Palazzo Serristori. Photo: renzodionigi, Flickr purple, when mixed with white, gave a very opaque glaze with the colour of a blueberry milkshake, admittedly very unlike the appearance of porphyry. Luca’s interest in imitating porphyry came later. The first occasion on which he sought to evoke the rock with his glazes was in the Pazzi coat of arms (Italian stemma) (c.1461), on the interior of the dome of the family chapel in the chapter house of Santa Croce in Florence. Given the commemorative character of the commission, it was highly appropriate to imitate the purple and durable porphyry. Undoubtedly, a family of such lofty aspirations as the Pazzi would have appreciated the long-standing connotations of the material with power and rule. However, only in the purple shell which decorates Jacopo Pazzi’s stemma (dated to 1460–1465), which was jointly executed by Luca and Andrea, can we observe significant technical progress in mimicking the visual properties of porphyry (fig. 3.4). This time there are clear white and black dots, to suggest that it is not just any purple, an artistic choice of the colour, but a conscious, deliberate attempt to imitate porphyry. Apart from the use of porphyry-like glazes for stemmi and decorations of commemorative spaces, the Della Robbia workshop imitated elements that could have been carved from the actual rock, such as pilasters, tombstones, or the thrones on which the Virgin was seated with her divine Son. In the Basilica at La Verna, Andrea della Robbia’s Assumption of the Virgin includes a detailed porphyry sarcophagus (fig. 3.5). Through the deliberately uneven application Bol_and_Spary_04_Sarnecka.indd 99 18 Aug 2022 3:07:25 pm 100 Sarnecka Figure 3.5 Andrea della Robbia, The Assumption of the Virgin, 1488 (detail), glazed terracotta La Verna, Santa Maria degli Angeli. Photo: Zuzanna Sarnecka Bol_and_Spary_04_Sarnecka.indd 100 18 Aug 2022 3:07:25 pm Firing Porphyry in the Italian Renaissance Kiln 101 of the manganese glaze, Andrea conveyed the actual characteristics of the porphyry, taking into account the fact that its crystals, depending on the type of porphyry used, could be white or, as in this case, slightly pinkish. Moreover, in this composition Andrea also juxtaposed purple porphyry with the green variant, also seen as a powerful religious symbol, and famously used in the thirteenth century for the tomb of St. Anthony in Padua (Lorenzoni 2000, 129). He clearly wanted to establish this symbolic connection and show the variety of materials obtainable through the glazing of terracotta. He repeated this juxtaposition of purple and green porphyry in other works, including the Lamentation over the dead Christ in the Old Cathedral at Marseilles, now in the sacristy of the new Cathedral. Certainly, Andrea was much more interested in imitating the actual properties of porphyry than his uncle, and it is in his works that we can find the best examples of mimesis of the material. In Luca’s Madonna del Roseto, dated to 1460–1470, now in the Bargello, we see a uniform, darker, porphyry-like glaze used in the throne. Andrea’s treatment of the same element in the Annunciation panel, held at the Bode Museum, captures the actual texture and visual properties of porphyry. In both instances, the material of the Virgin’s throne is bound to establish the connection between porphyry and rulership. Close-ups of the two reliefs reveal the dramatic difference in treatment of the same rock using the medium of glazed terracotta (figs. 3.6–7). The relief by Andrea, which might have been a part of a base of an altarpiece or a predella, as in another work by him designed for the Baglioni Chapel at Assisi and now held at the Museo della Porziuncola, includes white crystals and pinkish dots on the surface of the throne, combined with black short smudges to suggest the stippling typical of porphyry.33 In the scenes of the Assumption, Andrea also used porphyry-like glazes to adorn the Virgin’s sarcophagus. In the Madonna della Cintola with saints of c.1502, from the Collegiata of S. Martino e S. Leonardo at Foiano (fig. 3.8), we see the sarcophagus with three panels imitating red porphyry below the figure of the Virgin.34 On a different altarpiece in Frankfurt, there is a sarcophagus that only has two panels, showing the green and red porphyry. Andrea also included porphyry slabs in various predella panels – sometimes in rectangular or circular form. The latter was introduced in a laurel wreath in the altarpiece showing St. George fighting the dragon, at Pieve di S. Maria e S. Giorgio at Brancoli, dated c.1490–1500.35 Andrea’s sons echoed some of this ambition to imitate porphyry in their own work. Towards the end of the fifteenth century, Giovanni della Robbia (1469–1529) displayed this material in the architectural frame for the Lavabo, in Bol_and_Spary_04_Sarnecka.indd 101 18 Aug 2022 3:07:25 pm 102 Sarnecka Figure 3.6 Luca della Robbia, Madonna del Roseto, c.1460–70 (detail), glazed terracotta Florence, Bargello Museum. Photo: Zuzanna Sarnecka the sacristy of Santa Maria Novella in Florence (fig. 3.9). Similarly, in a ciborio for the sacred host at the Barga Cathedral, the artists of the Della Robbia workshop depicted porphyry on the bases of two angels bearing candelabras, dated c.1490–1500.36 Another ciborio for the sacred host, held at Isabella Stewart Gardner Museum in Boston, has spandrels with disks that juxtapose red porphyry against a green background on the right-hand side, and serpentine against a porphyry background on the left.37 The use of porphyry-like glazes in the context of a ciborio could have been stimulated by the artists’ ambition to evoke in their sculptures the links between porphyry and the sacrifice of Bol_and_Spary_04_Sarnecka.indd 102 18 Aug 2022 3:07:25 pm Firing Porphyry in the Italian Renaissance Kiln 103 Figure 3.7 Andrea della Robbia, The Annunciation, 1490 (detail), glazed terracotta Berlin, Bode Museum. Photo: Zuzanna Sarnecka Bol_and_Spary_04_Sarnecka.indd 103 18 Aug 2022 3:07:25 pm 104 Sarnecka Figure 3.8 Andrea della Robbia, Madonna della Cintola, 1502, (detail), glazed terracotta Foiano della Chiana, Collegiata. Photo: Zuzanna Sarnecka Figure 3.9 Giovanni della Robbia, Frame for the marble lavabo, c.1498 (detail), glazed terracotta Florence, Sacristy of Santa Maria Novella. Photo: Zuzanna Sarnecka Christ which allowed His body and blood to be transformed into bread and wine during the Eucharist. It should be emphasised that the imitation of porphyry in glazed terracotta was not limited to flat surfaces, but also included moulded elements. An altarpiece of the Assumption of the Virgin, attributed to the artist-friar Fra Ambrogio della Robbia (1477–1528), now in the Palazzo Comunale in Pergola, but originally in the Hermitage of the Minori Osservanti di San Giorgio at Monterubbio, has a frame decorated with porphyry vases in the form typical of the Della Robbia workshop (fig. 3.10).38 Ambrogio’s brother, Fra Mattia (1468– after 1532), addressed the needs of the Franciscan community by firing figures entirely in white, such as in The Annunciation, now in the Church of Santa Maria del Soccorso in Arcevia. This work is important for our understanding of Bol_and_Spary_04_Sarnecka.indd 104 18 Aug 2022 3:07:25 pm Firing Porphyry in the Italian Renaissance Kiln Figure 3.10 105 Fra Ambrogio della Robbia, Pala di Pergola, c.1520 (detail), glazed terracotta Pergola, Palazzo Comunale. Photo: Zuzanna Sarnecka Bol_and_Spary_04_Sarnecka.indd 105 18 Aug 2022 3:07:25 pm 106 Sarnecka the persistence of this signature colour in the Della Robbia shop in the Marche and the devotional connotations of this colour outside Florence, but it also includes a mimetic representation of porphyry in the spandrels of the Virgin’s bedchamber, thus confirming an interest in showing the material outside Tuscany as well. Over time, less attention was paid to material mimesis among the artists from the Della Robbia workshop. Girolamo della Robbia (1488–1566), when decorating the base of the statue of St. Francis, now in the Museo Bandini, applied the dark manganese-purple glaze unevenly onto the light surface of the fired terracotta, which in various areas comes through the glaze and creates a rather poor representation of the white crystals that are characteristic of porphyry (fig. 3.11). Moreover, the white glaze, which ran during the firing, splits the base through the middle and spoils the illusion, reminding the viewer that he or she is not actually looking at a piece of porphyry but at a piece of glazed terracotta. Imitating porphyry in glazes was not an easy or straightforward task, and clearly the Buglioni, the successors of the Della Robbia artists, had trouble in obtaining good effects when mimicking this material. As remarked by Allan Marquand, a sarcophagus in the scene of the Assumption of the Virgin Figure 3.11 Girolamo della Robbia, San Francesco, c.1510–15, (detail), glazed terracotta Fiesole, Museo Bandini, Fiesole. Photo: Zuzanna Sarnecka Bol_and_Spary_04_Sarnecka.indd 106 18 Aug 2022 3:07:25 pm Firing Porphyry in the Italian Renaissance Kiln 107 by Benedetto Buglioni (1459/1460–1521) from the church of Santa Maria a Casavecchia was merely a ‘mottled violet in imitation of porphyry or marble’.39 Through their use of porphyry-like glazes, members of the three generations of the Della Robbia family established the spiritual connotations with blood and rulership, as well as evoking the hardness of the material transformed by heat in a little-known process. They imitated the aesthetic properties of porphyry in three major respects: the rock’s deep purple colour, its texture, which included stippling, and its lustre. The exercise of imitating porphyry shows that Luca and later Andrea della Robbia were truly in the vanguard of the Florentine era of experimentation. In Florence under Medici patronage, over the course of the sixteenth century, it became increasingly popular to imitate porphyry in paint. Without true knowledge of the origin of porphyry or the tools to shape it, the Della Robbias’ glazed terracotta was the best available substitute for the actual stone, becoming porphyry in every aspect but its chemical composition. Secrecy and lack of knowledge of the material were key to creating a mythology for both glazed terracotta and porphyry. Cultural, artistic and social factors meant that the Della Robbia family’s interest in porphyry occupied a unique place in their practice. Manmade porphyry, created in the new, quasi-magical medium, added symbolic and religious value to the Della Robbia sculptures. Luca and Andrea – like Christ during the Wedding at Cana – transformed liquid matter into something else, if in their case the result was not wine but hard and precious porphyry. Acknowledgements I am very grateful to Professor Deborah Howard, my colleagues from the University of Warsaw and the editors for their most helpful comments on the earlier versions of this chapter. The final stage of my research was generously supported by the National Science Centre, Poland (Project no. 2018/29/B/ HS2/00575). Bibliography Aligheri, Dante, Purgatorio (D. Provenzal, ed.), Verona 1949. Barbour, Daphne & Roberta Olson, ‘New methods for studying serialization in the workshop of Andrea della Robbia. Technical study and analysis’, 56–61, in: Della Robbia dieci anni di studi-dix ans d’études (A. Bouquillon et al., eds.), Genoa 2011. Bol_and_Spary_04_Sarnecka.indd 107 18 Aug 2022 3:07:25 pm 108 Sarnecka Barry, Fabio, Painting in stone. The symbolism of colored marbles in the visual arts and literature from Antiquity until the Enlightenment, unpublished doctoral dissertation, University of Columbia 2011. Baxandall, Michael, Giotto and the orators. Humanist observers of painting in Italy and the discovery of pictorial composition 1350–1450, Oxford 1971. Bellandi, Alfredo, Catalogue entry, 123–126, in: cat. Fano, Tardogotico e Rinascimento a Pergola. Testimonianze artistiche dai Malatesta ai Montefeltro (M. Baldelli, ed.), Fano 2004. Bol, Marjolijn, ‘Polito et claro. The art and knowledge of polishing, 1100–1500’, 223–257, in: Gems in the early modern world: materials, knowledge and global trade, 1450–1800 (M. Bycroft & S. Dupré, eds.), Basingstoke 2018. Butters, Suzanne, The triumph of Vulcan: sculptors’ tools, porphyry and the prince in ducal Florence, Florence 1996. Carruthers, Mary, The craft of thought: meditation, rhetoric and the making of images 400–1200, Cambridge 1998. Cat. London, British Museum, Treasures of heaven. Saints, relics and devotion in medieval Europe (M. Bagnoli et al., eds.), London 2011. Cennini, Cennino, Cennino Cennini’s Il libro dell’arte. A new English language translation and commentary and Italian transcription (L. Brocke, trans.), London 2015. Conway, William M., ‘The Abbey of Saint-Denis and its ancient treasures’, Archeologia, 16 (1915), 103–158. Didi-Huberman, Georges, Fra Angelico: dissemblance and figuration, Chicago & London 1995. De Clavijo, Ruy González, Embajada a Tamorlán (F. López Estrada, ed.), Madrid 1999. De Clavijo, Ruy González, Narrative of the embassy of Ruy Gonzalez de Clavijo to the court of Timour at Samarcand, A.D. 1403–6 (C. Markham, ed.), London 1859. Del Bravo, Carlo, ‘L’umanesimo di Luca della Robbia’, Paragone, 285 (1973), 1–34. Del Bufalo, Dario, Porphyry. Red imperial porphyry. Power and religion, Turin, London, Venice & New York 2012. Delbrück, Richard, Antike Porphyrwerke, Berlin 1932. Eamon, William, Science and the secrets of nature: books of secrets in medieval and early modern culture, Princeton 1994. Favreau, Robert, ‘Les autels portatif et leurs inscriptions’, Cahiers de civilisation médiévale, 56 (2003), 327–352. Filoramo, Giovanni, ‘Variazioni simboliche sul tema della porpora nel Cristianesimo’, 227–242, in: La porpora: realtà e immaginario di un colore simbolico (O. Longo, ed.), Venice 1998. Garzelli, Annarosa, Miniatura fiorentina del rinascimento 1440–1525. Un primo censimento, vol. 2, Florence 1985. Bol_and_Spary_04_Sarnecka.indd 108 18 Aug 2022 3:07:26 pm Firing Porphyry in the Italian Renaissance Kiln 109 Gavel, Jonas, Colour. A study of its position in the art theory of the quattro- & cinquecento, Stockholm 1979. Gentilini, Giancarlo, I Della Robbia, Florence 1992. Hankins, James, ‘Ptolemy’s Geography in the Renaissance’, in: Humanism and platonism in the Italian Renaissance (J. Hankins, ed.), vol. 1, Rome 2003. Ligorio, Pirro, ‘Delle antichità di Roma’ (1553), Libro XXXVI, ‘varij Marmi e Colori di quelli’, Ms. Oxford, Bodleian Library, Ms. Canonici Ital. 38, ff. 108r/v. Long, Pamela, Openness, secrecy, authorship: technical arts and the culture of knowledge from Antiquity to the Renaissance, Baltimore 2001. Lorenzoni, Giovanni, ‘Le vie del porfido a Venezia. Gli amboni di San Marco’, 299–316, in: Le vie del medioevo (A. C. Quintavalle, ed.), Milan 2000. Malgouyres, Philippe, Porphyre. La pierre pourpre, des Ptolémées aux Bonaparte, Paris 2003. Marini, Marino, ‘Le “terracotta robbiana” e la maiolica a Firenze nel primo Rinascimento’, 55–61, in: I Della Robbia. Il dialogo tra le arti nel Rinascimento (G. Gentilini, ed.), Milan 2009. Marquand, Allan, Atelier of Andrea della Robbia, vol. 2, New York 1972. Marquand, Allan, Andrea della Robbia, Princeton 1922. Merrifield, Mary P., Medieval and Renaissance treatises on the arts of painting, Mineola, NY, 1999 [orig. 1849]. Minelli, Alessandro, ‘Zoologia della porpora’, 67–78, in: La porpora: realtà e immaginario di un colore simbolico (O. Longo, ed.), Venice 1998. Mundy, James, ‘Porphyry and the “posthumous” fifteenth-century portrait’, Bruckmanns Pantheon, 46 (1988), 37–43. Newman, William, ‘Art, nature, and experiment in alchemy’, 304–317, in: Texts and contexts in ancient and medieval science (E. Scylla & M. McVaugh, eds.), Leiden 1997. Piccolpasso, Cipriano, The three books of the potter’s art (R. Lightbown & A. Caiger-Smith eds.), vol. 2, London 1980. Planiscig, Leo, Luca della Robbia, Florence 1948. Pliny the Elder, The natural history (J. Bostock, ed.), London 1855. Poggi, Giovanni, Il Duomo di Firenze. Documenti sulla decorazione della chiesa e del campanile, tratti dall’archivio dell’opera, vol. 2, Florence 1988. Pope-Hennessy, John, Luca della Robbia, Oxford 1980. Raff, Thomas, Die Sprache der Materialien. Anleitung zu einer Ikonologie der Werkstoffe, Münster 2003. Renna, Enrico, ‘Ricette per succedanei della porpora in due papiri greci’, 133–147, in: La porpora: realtà e immaginario di un colore simbolico (O. Longo, ed.), Venice 1998. Rucellai, Giovanni, Giovanni Rucellai ed il suo zibaldone (A. Perosa, ed.) London 1960 (orig. 1457). Bol_and_Spary_04_Sarnecka.indd 109 18 Aug 2022 3:07:26 pm 110 Sarnecka Salvadori, Monica, ‘Ante omnes est purpurissum. La porpora nella pittura parietale Romana’, 203–225, in: La porpora: realtà e immaginario di un colore simbolico (O. Longo, ed.), Venice 1998. Sarnecka, Zuzanna, The Della Robbia and glazed devotional sculpture in the Marche, unpublished doctoral dissertation, University of Cambridge 2017. Sarnecka, Zuzanna, ‘Luca della Robbia and his books. The Renaissance artist as a devotee’, Artibus et historiae, 74 (2016), 291–301. Scholten, Frits, ‘Bronze, the mythology of a metal’, 20–35, in: cat. Leeds, Henry Moore Institute, Bronze. The power of life and death (M. Droth & P. Curtis, eds.), Leeds 2005. Smith, Pamela H., The body of the artisan. Art and experience in the Scientific Revolution, Chicago 2004. Theophilus, The various arts (C. R. Dodwell, trans.), London 1961. Tronzo, William, ‘Medieval porphyry. The subliminal narratives of a material’, 45–53, in: Le plaisir de l’art du Moyen Âge (R. Alcoy, X. Barral i Altet, D. Allios & M. A. Bilotta, eds.), Paris 2012. Vasari, Giorgio, Le vite de’ piú eccellenti architetti, pittori, et scultori italiani da Cimabue insino a’tempi nostri 1550 (L. Bellosi & A. Rossi, eds.), Turin 1986. Vasari, Giorgio, Le Opere di Giorgio Vasari con nuove annotazioni e commenti di Gaetano Milanesi, vol. 1, Florence 1973. Ward-Perkins, John B., ‘Quarrying in Antiquity: technology, tradition and social change’, Proceedings of the British Academy, 57 (1971), 137–158. Endnotes 1 2 3 4 5 6 7 8 9 10 Pirro Ligorio, ‘Delle antichità di Roma’, Libro XXXVI, ‘varij Marmi e Colori di quelli’, Oxford, Bodleian Library, Ms. Canonici Ital. 38, ff. 108r/v: ‘Il Porphirite […] quando il volemo contrafare in pittura noi facemo un campo di color tarrè [sic] òver lionato rossetto, ma che habbi del scuretto, et dopo con color di carne li buttamo sopra certi punti minuti col pennello’. Gentilini 1992, 12; Del Bravo 1973, 1–34. Aligheri 1949, Canto IX, 101–102, 389: ‘porfido mi parea sí fiammeggiante / come sangue che fuor di vena spiccia’. Aligheri 1949, Canto IX, 95–96, 389: ‘marmo bianco era, sí pulito e terso ch’io mi specchiai in esso qual io paio’. For the significance of Dante’s writings for Luca’s sculptures, see Sarnecka 2016, 291–301. New International Version. Cat. London 2011, no. 42. Ms. Thompson 30, f. 37; Garzelli 1985, 663, fig. 1059. Rucellai 1960, 74: ‘molte belle tavole di porfido et maxime sotto il pergamo, rilucenti come uno specchio, delle più belle che sieno in Roma’. Barbour & Olson 2011, 56–61, tab. 2b. Barry 2011, 67; Raff 2008, 134–142. Bol_and_Spary_04_Sarnecka.indd 110 18 Aug 2022 3:07:26 pm Firing Porphyry in the Italian Renaissance Kiln 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 111 Delbrück 1932, xix, 2, 31, 134. Vasari 1973, 109–111: ‘A’ dì nostri non s’é mai condotto pietre di questa sorte a perfezione alcuna, per avere gli artefici nostri perduto il modo del temperare i ferri, e così gli altri strumenti da condurle’. Cennini 2015, chap. XXXVI. Barry 2011, 497; Butters 1996, 171, 334–335. Pope-Hennessy 1980, 15–16; Del Bravo 1973, 1–34. Long 2001. On openness in Theophilus’s practice, see 85–88; for Biringuccio, 178–179; for Piccolpasso, 234–235. On artisanal secrecy in the early modern period, see Eamon 1994; Newman 1997; Smith 2004. Pope-Hennessy 1980, Appendix II, 91–93. De Clavijo 1999, 130 and note 109: ‘E entre ellos avia cuatro màrmoles muy grandes, las dos, a la una parte derecha, e las otras dos a la otra parte siniestra, que eran coloradas de una cosa que es fecha de polvos arteficialmente e llámanlo pílfido’. Butters 1996, 43. Her interpretation is the more striking in that she included in her Appendix V and VI, 398–403, a range of documents showing that in the mid-sixteenth century there was still no understanding of how columns could have been carved in porphyry, and that the tools to work the rock were rediscovered only in the second half of the sixteenth century. Barry 2011, 288. Piccolpasso 1980, c.64r: ‘Fatto tutto questo porgonsi preghi a Dio con tutto il core ringratiandolo sempre di tutto cio chegli ci da’. Piccolpasso 1980, c.64v: ‘Racordandosi far sempre tutte le cose col nome di Jesu Cristo acceso il fuoco’. Cennini 2015, chap. CLXXII. Theophilus 1961, preface to the third book, 62. In the Middle Ages, similar links were drawn between rhetoric and piety (Carruthers 1998, 9). Baxandall 1971, 152–154: ‘[…] porphyreticum pulchrum, et tornatile’. New International Version. There are other instances of porphyry vases preserved in churches across Europe that were believed to have been those in which Christ transformed water into wine at the Wedding at Cana; for a famous example at Saint-Denis, see Conway 1915, 103–158. Mundy 1988, 37–43. Sarah K. Kozlowski is currently working on a group of portable, multi-part panel paintings from Angevin Naples, painted on their exteriors to resemble porphyry. Piccolpasso 1980, c.26r: ‘Il manganese se ne trova abondante mentre per questo felicissimo stato et in diversi luoghi per la Toscana questo e notissimo per tutto Italia et operarsi per tutto ove si lavora di vetro’. Gentilini 1992, 11. On the trade in the dye see Renna 1998, 133. Poggi 1988, 21, doc. no. 1563: ‘[…] quod mons sit sui coloris arbores etiam sui coloris’. Gentilini 1992, 94. Marquand 1922, cat. no. 69, 102, fig. 72. Marquand 1922, cat. no. 354, 199–201, fig. 259. Marquand 1922, cat. no. 252, 125–127, fig. 209. Marquand 1972, cat. no. 213, 88–89, fig. 184. Marquand 1972, cat. no. 218, 91–92, fig. 186. Bellandi 2004, 123–126. Marquand 1972, cat. no. 114, 102–103, fig. 78. Bol_and_Spary_04_Sarnecka.indd 111 18 Aug 2022 3:07:26 pm Bol_and_Spary_04_Sarnecka.indd 112 18 Aug 2022 3:07:26 pm