A ‘milky mass’ and ‘uniform material’: white marble in eighteenth-century French discourses on sculpture and geology

Knowledge of the materiality of stone during the Enlightenment expanded following the exploration of mineralogical structure, to alter ideas about taxonomy and challenge the role of rocks in the history of the earth. Close studies of the material of marble sculpture generated expertise on grain size, surface varieties and stone deposits. This mode of reception became intertwined with contemporary controversies about the age of the earth. This article focuses on both French sculpture and geological discourses of the eighteenth century to reveal an international and interdisciplinary network centring on protagonists such as Denis Diderot, Paul-Henri Thiry d’Holbach and Étienne-Maurice Falconet; through these figures, debates can be connected concerning both geology and art theory. Within these contexts, the article discusses the translation processes between these artistic and geological interests.

Thorvaldsen’s marble connections

Although one of the most celebrated sculptors of the nineteenth century, little is known about Bertel Thorvaldsen’s relationship with the white marble he sculpted from. Today, scholars generally accept that Thorvaldsen knew how to sculpt in marble; however, for many years - including during his own lifetime - people regarded his investment in the white stone as somewhat detached. Taking the debate around Thorvaldsen’s marble-carving skills as a point of departure, this article analyses the evidence at hand: the marble sculptures themselves as preserved in the Thorvaldsen Museum in Copenhagen. Exploring the preserved surface textures on selected marble works, this article argues that Thorvaldsen engaged and experimented with different types of textural effects and marble types, revealing a yet unseen sensitivity towards the historic and symbolic significance layered in the stones themselves.

Impure stone and the threat to decency: marble tints and veins

According to the classical tradition, marble sculptures were to be made of ‘pure’ white material. This remained an aesthetic ideal even after archaeological findings had revealed evidence of ancient polychromy. This article argues that tinting as well as natural staining on marble figures in the late eighteenth and nineteenth centuries were not only aesthetically but also morally reprehensible, because they violated the ideal of homo clausus. This term, coined by the sociologist Norbert Elias, conceptualizes a subject that imposes ‘self-restraint’ to control its physical body and its emotions. Perfect control was seen embodied in the ancient images of the gods, which were assumed to have been made of immaculate white marble. Any colouring, whether of natural origin or deliberately produced, seemed to contaminate this concept. My investigation is focused on the historical justifications for John Gibson’s scandalous Tinted Venus, and figures of veined marble rejected in France on similar grounds in the late eighteenth century, such as Christoph-Gabriel Allegrain’s Venus and Jean-Antoine Houdon’s Frileuse. I examine how the coloured veins and tints of the stone gained semantic qualities in female figures, where a blush or a vein seemed to reveal emotions and desires and thus infringe the ideal.

Mineralogical Insights to Identify Göktepe Marble in the Sculptural Program of Quinta Das Longas Villa (Lusitania)

This archaeometric study is focused on the marble used in a group of fragmented sculptures found at the Roman villa of Quinta das Longas (Elvas, Portugal). Dating from the 4th century AD, the pieces are of remarkable quality and correspond to ideal and mythological figures from several iconographic cycles. The numerous fragments, all of very fine-grained white marble, are associated with the ornamentation of an impressive nymphaeum of the villa. Their high level of sculpture technique and style, the models followed and their similar typology to other well-known parallels raise the hypothesis of being linked with Aphrodisian workshops. Using a well-established multi-method approach, with Optical microscopy, X-ray Powder Diffraction (XRPD), qualitative and quantitative cathodoluminescence (CL) by CL-Optical and CL-SEM, and stable C and O isotopic and trace element analytical techniques (IRMS and ICP-AES), together with complementary parameters obtained from electron paramagnetic resonance (EPR) and 87Sr/86Sr isotopes, the marble provenance can be identified with certainty. The results all point to the best quality of white Göktepe marble, confirming the stylistic connection to the ancient Carian sculptors.

The Colors of the Circus Mosaic from Barcino (Roman Barcelona): Characterization, Provenance, and Technology Issues

Archaeometric studies on mosaics often concentrate only on glass tesserae, while comprehensive studies including both stone and glass tesserae are scarce; however, both types of tesserae can sometimes bring relevant data to elaborate archaeological knowledge on a studied mosaic. In this paper, a representative set of tesserae from a large polychrome Roman mosaic retrieved in Barcelona (NE Spain) is investigated using various methods. Most of the techniques were directly applied on samples prepared as petrographic thin sections (including polarized-light, cathodoluminescence and electron microscopies, and synchrotron through-the-substrate μX-ray diffraction). The results indicate that, from the ten sampled stone tesserae, there are (i) seven limestones, one of them identified as Alveolina limestone (early Eocene) from the southern Pyrenees (ii) two sandstones from Barcelona’s Montjuïc hill (Miocene) and, (iii) a Carrara white marble from the Apuan Alps (Italy). The profuse presence of tesserae of both local and imported materials with well-known uses in architecture, epigraphy, and sculpture could imply that tesserae were a by-product of their main use. Two different production technologies were identified for the three sampled glass tesserae. The concurrent use of antimony- and tin-based opacifiers is in agreement with the accepted archaeological chronology of the mosaic (4th century AD).

An improved QPSO-SVM-based approach for predicting the milling force for white marble in robot stone machining

Milling force prediction is one of the most important ways to improve the quality of products and stability in robot stone machining. In this paper, support vector machines (SVMs) are introduced to model the milling force of white marble, and the model parameters in the SVMs are optimized by the improved quantum-behaved particle swarm optimization (IQPSO) algorithm. A set of online inspection data from stone-machining robotic manipulators is adopted to train and test the model. The overall performance of the model is evaluated based on the decision coefficient (R2), mean absolute percentage error (MAPE) and root mean square error (RMSE), and the results obtained by IQPSO-SVM are superior to those of the PSO-SVM model. On this basis, the relationship between the milling force of white marble and various machining parameters is explored to obtain optimal machining parameters. The proposed model provides a tool for the adjustment of machining parameters to ensure stable machining quality. This approach is a new method and concept for milling force control and optimization research in the robotic stone milling process.

A Jesus of White Marble or a Jesus in the Flesh?

Despite the early loss of his Christian faith, Renan held onto a lifelong belief in the incommensurability of Christianity with Judaism and Islam. This entailed his perception of an unbridgeable chasm between Christianity and the two “Semitic religions.” Such insistence originated in his understanding of Jesus as a unique figure, one who stood at the very core of the world history of religions. It is in his Life of Jesus that he expressed most clearly his views on the founder of Christianity. First published in 1863, Renan’s Vie de Jésus would swiftly become, in the original as well as in its multiple translations, a nineteenth-century international best seller. The chapter reassess the roots of Renan’s project, as well as its impact. Finally, we compare Renan and the Jewish historian Joseph Salvador on the figure of Jesus.