Sculpture, Polychromy, and Architectural Decoration Polychrome Sculpture: Decorative Practice and Artistic Tradition Tomar, May 28-29 2013
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ICOM-CC Working Group: Sculpture, Polychromy, and Architectural Decoration Polychrome Sculpture: Decorative Practice and Artistic Tradition Tomar, May 28-29 2013 Papers Geopolymers: potential use in sculpture restoration. João Coroado Email: [email protected] Departmental Unit of Archaeology, Conservation and Restoration and Heritage/GEOBIOTEC & Polytechnic Institute of Tomar, Quinta do Contador - Estrada da Serra 2300-313, Tomar, Portugal. The ‘alkali activated’ or ‘geopolymers’ have been studied since 1950s and, until now, many applications have been tested with success and advantages compared with traditional applications. In the scope of conservation of terracotta sculpture some advances have also been reported. Geopolymers are formed by partial dissolution of alumino-silicate powders, often characterised by a high degree of amorphous phase and subsequent repolymerisation. At a relative low temperature, the rising chains of an alkali-aluminosilicate gel phase finish by hardening of a mainly amorphous three-dimensional net with bonded inclusions of unreacted solid precursor particles. Much of the interest in the study of this group of materials is the high possibility of using different raw-materials that enable the formations of geopolymers. In this context, the approach covers firstly a short history of geopolymer science, secondly the chemistry that is involved in the geopolymerisation process and the raw materials characteristics, and finally the properties and applications of geopolymers, with special attention to the potential applications in the conservation of terracotta sculpture. Polychrome coatings on a lime plaster altarpiece (1571): the Gaspar Fragoso chapel in Portalegre. Patrícia Alexandra Rodrigues Monteiro Email: [email protected] PhD Candidate, Researcher of the Art History Institute of the Faculty of Letters of the Lisbon University, R. Capitão Leitão, n.º 42, 1.º, 1950-052 Lisbon, Portugal. The long history of altarpieces constructed in order to imitate other materials begins in the city of Portalegre, in the northern Alentejo region, with the example of the Gaspar Fragoso chapel (1571). This altarpiece remains as a unique exemplar of a tradition that was subsequently developed throughout the seventeenth and eighteenth centuries in more complex altars, usually painted and gilded. The Portuguese altarpieces modelled in plaster-like mixtures based on slaked lime and sand as main components followed the very evolution of national altarpieces carved in wood or stone. The decorative layers, with polychrome or gilded finishes, emulated the techniques used to decorate these more traditional supports. The Alentejo has, still today, a substantial artistic patrimony where a material such as slacked lime always prevailed throughout the centuries used in several ways and hence with different aggregates. In fact, the extraordinary versatility of lime enabled, in this same region, the development of different artistic and decorative techniques (such as mural paintings, sgrafittos, decorative lime plasters and mortars, etc). In addition, the Alentejo is well known for its whitewashed façades. In parallel, altarpieces constructed in slaked lime and sand plasters (as mouldable pastes) were very common in this part of the country, namely in the Portalegre district. Literature reports the steps of application of different material for building this type of altarpiece decoration: a first layer composed by slacked lime and coarse sand was applied onto a brick structure; then it was covered with a thinner layer with fine sand, sometimes with additives (marble flour, gypsum, etc). The finishing layers applied to these works included polishing, painting and also gilding. Today there are still many of such altarpieces, scattered somewhat by churches and chapels from the sixteenth until late eighteenth centuries. Despite its large number, these artworks constitute a group difficult to characterise both for their heterogeneity from the artistic point of view and also for their unknown authorship. The increasing number lime plaster altarpieces with painted or gilded coatings constructed from the sixteenth century onwards suggests a very particular artistic taste growing in northern Alentejo. These artworks were elaborate and of high quality. Subject to systematic and poorly executed repaints, this artistic heritage now remains much altered resulting in severe losses of the formal characteristics. The altarpiece in the Gaspar Fragoso Chapel was constructed using lime plaster modelled in high relief directly in the wall. A thin finishing coating of undetermined composition was subsequently applied and painted. The unusual appearance of this altarpiece has led to a misunderstanding: it was thought that the altar was sculpted in limestone like the contemporary pieces found in the region of Coimbra. This proves the illusory potential of this type of mouldable mixtures when used to construct such artworks, an illusion that continues to surprise after almost five centuries. There are still questions that remain without answer, such as the identity of the artists involved in these artworks, where they came from and their artistic background. Their work remains, however, as a proof of deep-rooted artistic traditions. Materials, techniques and degradation products of the 15th Century Burgundian polychrome-stone sculpture in Aragon and Navarra (Spain). Some issues for the development of cleaning protocols. E. Aguado-Guardiola1*, P. Cremonesi2, X. Màs–Barberà3, D. J. Yusá-Marco3 * Author for correspondence Email: [email protected] 1. Conservation and Restoration of Cultural Heritage College of Aragón, Coso Alto 61 (Edif. Capuchinas), 22003 Huesca, Spain. 2. Free-lance conservation chemist, Via Pascoli 1, 26854 Cornegliano L., Italy. 3. Universitary Institute of Restoration of Cultural Heritage, Edificio B-Acceso K- Planta 0. Universidad Politécnica de Valencia. C/Camino de Vera, s/n. 46020- Valencia, Spain. This research explores which factors may influence the transformation that polychromies on stone undergo in time. Two case studies will be used for this purpose: the tomb of Villaespesa Chancellor in the Cathedral of Tudela (Spain), and a sculpture from the altarpiece of Los Corporales Chapel in the Church of Santa María in Daroca (Spain). They were constructed, respectively on sandstone and on limestone, and painted with oil and protein binding media in the beginning of the fifteenth century. The artisans creating these works were trained, either directly or indirectly, in the avante- guard style typical of Burgundian polychrome stone sculpture found at the Claus Sluter and Jean Malouel Workshops in the Chartusian monastery at Champmol, near Dijon (France). In this study, materials and painting techniques as well as aging effects, have been studied for both sculptures. Binders, fillers, pigments and some degradation products have been characterised. Glass slides, as well as mock-ups made from the same types of stone, were painted simulating the material combinations commonly found in both case studies. It is well known that the aging of binders, fillers and paint mixtures on stone do not generate the same degradation products as they do on wood or other organic supports. On stone, the same aging processes may give rise to new, and sometimes unexpected, products of inorganic, organic or mixed nature. The reaction mechanisms that explain the formation of oxalates and other metal salts or soaps, remain partly unexplained: especially with regard to the chemical reactions involved in the mineralization of polychromies on the most characteristic varieties of stone, typically used in sculpture. In addition, from a thermodynamic and stoichiometric point of view, the origin of some low molecular weight products, such as oxalic acid, is not well understood yet. These by- products may derive from materials present in the sculpture or from the surrounding environment. When reacting with some of the constituent materials, these yield new compounds of different chemical composition and physical properties. It may even be possible that scientific analysis could no longer detect the presence of some of the original binders used by the artisan, as it happens with hide glue, due to their transformation into new degradation products. All these transformations result in drastic changes in the physical-chemical nature of the paint layers of stone sculptures. Such changes can strongly influence their aesthetic appearance as well as their durability. For this reason, conservation of these surfaces should be aimed at establishing protocols that appreciate the complexity of their changing nature, determine the potential risks posed by conservation materials and methods to the constituent materials of the work of art, and take into account which reactions could likely take place in the mid-to-long term, under different environmental conditions once the conservation treatment has been completed. Comparative analysis of the actual case studies and of the models considered in this research will stimulate new work hypotheses, and will allow the understanding of both the production and the aging mechanisms of these artworks to deepen. This study will constitute a preliminary step to understanding their degradation and lead to devising protocols for both intervention and preservation. Study and conservation of a polychrome terracotta sculpture from the Casa- Museu José Régio – a first step towards the characterisation of the Barros de Portalegre. Francesca