Project

The monumental terracotta sculptures from the Alcobaça Monastery, mostly produced by the monks of the Cister Order during the last third of the 17th century, are one of the most important sets and original works of art from this period, both aesthetically and technically recognized by Portuguese and international historiography. Integrated in a UNESCO World Heritage monument since 1989, they acquired visibility both for this reason and due to their dimensions, each circa 2 metres (6.6 feet) high.

At the present time these sculptures are in a very frail state, and their visibility has been compromised by poor preservation conditions, which put them in a serious risk of total loss. Contributors for this situation are mainly the terracotta material alterations, provoking a total loss of cohesion, causing polychromy desegregation and parts to frequently fall apart. Some attempts to mitigate the degradation process forced several interventions to take place during a two centuries time span, interventions that proved not successful.

The aim of this project is to comprehend the alteration processes of this monumental terracotta sculptures from the Alcobaça Monastery, and further allowing a future sustainable conservation intervention. A second objective, that will support the intervention, is the investigation and development of compatible mineral consolidants based in geopolymer composites, with properties that can meet the necessary criteria for a proper conservation intervention. For these objectives to be met, studies, analysis and testing will take place oriented by four complementary action guidelines:

1. Historical and artistic study of the pieces in the Portuguese and European context of the 17th century terracotta sculptures, with particular attention to the high-chapel set. To fulfil this purpose, an archival research will be made in the “fundos alcobacenses” (primary sources) existent both in the Biblioteca Nacional de Portugal (Portuguese National Library) and in the Instituto dos Arquivos Nacionais Torre do Tombo (National Archives), as well as in other and later (mainly from the 19th and 20th centuries) documents existent in the Alcobaça archives. Comparative studies of similar production areas in Spain (Sevilla), Italy (Turin) and France (Main and Anjou) will also be carried out. From this investigation the team hopes to acquire information related with the clay raw-material exploration and ceramic transformation activity in Alcobaça region, and the commerce of pigments used in the sculptures polychromies.

2. Characterization of the ceramic supports composition, the raw clay material provenance (geological context). The determination of the thermal transformations that occurred in mineral phases during the ceramic body production and investigation of the reactions that originated the current loss of cohesion, will be studied through samples analysis from the sculptures and clay raw material from the Monastery neighbourhood, after thermal transformation and accelerated aging in climatic chambers, with the same properties as the terracotta from the sculptures. To answer these problems several analytical methods will be used: for the study of ceramic and clay raw materials X-ray diffractometry (XRD), wavelength dispersive X-ray fluorescence spectrometry (WDXRF) and scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDS) will be employed. The results, namely those relating to the elemental composition, will be treated by multivariate statistical analysis (such as grouped and principal component analysis) in order to find similarities that can help in the determination of the raw materials sources.

3. Study of the several layers existent over the ceramic body, namely the polychromatic ones, and the preparation layer. This involves the identification and characterization of pigments, specially the mineral inorganic ones, and the gold leaf, both applied through time in several strata. This data will be very important to compare and look for specificities with ones used in canvas and wood supports. The polychromy analysis will be carried out in situ with the use of non-intrusive techniques such as colorimetry and energy dispersive X-ray micro-fluorescence spectrometry (µ-EDXRF). Materials characterization will be complemented with a micro-sampling study, which will also allow the classification of the several layers preservation status. These micro-samples will be studied by optical, spectrometric and diffractometric techniques.

4. Investigation and development of inorganic consolidants, based in metaKaolinite geopolymeric composites. These need to confirm the necessary properties that enable their application as consolidants of works of art compatible with the system constituents and their respective physical, chemical, mechanical and aesthetical properties. In addition to the necessary procedures and analysis for obtaining those consolidants, compatibility tests will be performed to aged samples that show similar degradations that the original sculptures. The evaluation will be done before and after the aging tests applied to samples treated with those consolidants. An “in situ” model of a conservation intervention will be completed in order to show and make the results known to the public in general. A diffusion campaign will be organized with the purpose of alerting the community for the heritage conservation problems, enabling, and facilitating their involvement in the safeguard of this important cultural heritage. The results achieved by the project will also be disseminated through seminars of specific and general scales in order to contribute to the preservation of the local collection of terracotta sculptures.