Plan and methods

The project will begin with a literature review carried out in several sources, kept both local and in the Portuguese National Library and National Archive Torre do Tombo (NATT). In addition to the information provided about historic and artistic features, this research will furnish information about the sculptures production and the usual places of extraction of raw materials specially in the 16th and 17th centuries.

Also in the beginning, the diagnosis task will begin with the photographic and graphic record of the sculptures. Prospecting windows, through the whitewash lime layer applied last century during the middle of 50's for the polychromy protection, will be opened to know its conservation appearance. A device for environment monitoring will be placed near the sculptures for the continuous evaluation of the environmental parameters fluctuations, namely thermal, hygrometric and light fluctuations devise.

After the prospecting and registering tasks, "in situ" analysis by EDXRF, colorimetry and micro-sampling procedure will begun in the prospecting windows where the polychromy will be exposed. Microsampling for laboratorial testing will be done during and afterwards this analysis. The samples will be taken from the polychrome layers and they will be used in the study of the stratigraphy and in other analyses necessary to the pigment identification.

The samples from the polychromy will be analysed by reflected light microscopy, for the stratigraphic study; polarized light optical microscopy (PLOM), for the mineral composition study; micro X ray diffractometry (µXRD), for the characterization of crystalline phases; micro-energy dispersive X ray fluorescence spectrometry (µEDXRF), for qualitative and quantitative elemental analysis; scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), for the observation of textured details and semi-quantification of the chemical elements and µFourier transform infrared spectroscopy (µFTIR). These equipments are availablmicro- from the laboratories involved in the project and slould be complemented with fluorescence light optical microscopy (MOLF) mainly for the gold leaf study.

To complete the analytical information, other complementary techniques should be used, such as synchrotron radiation µ-X ray diffractometry (SR-µXRD), micro-tomography (µTomography), and X ray absorption spectroscopy (µXANES). These equipments are in ISAS (Institute for Analytical Sciences) and in DELTA (Synchrotron beam line at the University of Dortmund, Germany) laboratories.

Samples in different conservation conditions also will be sampled from the terracotta ceramic support.

At the same time as the sculpture sampling, clay samples will be collected in local clay-pits, selected in accordance with the information provided by documental sources, and analysed, in laboratories of the GeoBioTec investigation centre. Their compositional characterization will be done as the sculpture's supports characterization with X rays diffraction (XRD), wavelength dispersive X rays fluorescence (WDXRF) and SEM/EDS.

A comparison between analytical data obtained from raw materials and sculptures will be made in order to enable the identification of possible provenances of the materials. For that purpose statistical multivariate analysis, namely numerical taxonomy and principal components analysis, will be applied.

Samples for technological studies and aging tests will be taken from clay-pits marked as sources of raw materials. The clay preparation, the plastic conformation and the firing procedure at different temperatures will be made at Centro Tecnológico da Cerâmica e do Vidro (Glass and Ceramic Technological Centre) (CTCV). After technological characterization after firing at different temperatures (retraction, mechanical bending strength, water absorption, and crystalline phases formation by DRX) the proof bodies will be submitted to accelerate aging tests in climatic chambers. Those that show alterations similar to those of the sculptures will be tested with the mineral consolidants previously developed.

The development of the consolidants will be made at GeoBIoTEc laboratories based in metakaolinite (and other clay minerals) geopolymers composites. The consolidants properties should have very good fluidity and a slow consolidant action to avoid the formation of horizons with different behaviour to the external solicitations. After the application, the consolidant has to allow the permeability to the water vapour, has to be resistant to the UV radiation, don't stain and must be compatible with the original materials. This stage focuses on achieving a pozolanic reaction between the ceramic mass and an engineered fluid with a reactive material. It will be develop a suspension based on geopolymer composite solute, adapted at the porosity, namely micro and open porosity, of the terracotta sculptures, with good penetration capacity (velocity and depth) through the permeable ceramic medium. The volumetric variation due the "anchorage or lashing" process, developed inside the ceramic material, must be monitored during the kinetics of the hardening reaction.

The intervention on the sculptures will be done in situ, with the complete removal of the whitewash layer and the stabilization of the polychrome layers, after that the selected mineral consolidant solution. A restoration intervention will be made with ceramic previously moulded and fired with a compatible clay paste. Finally, the reintegration with mineral pigments will conclude the conservation and restorations intervention. An impermeable base will be design for which sculpture to avoid the ground capillarity that affect the base of sculptures.

This project will allow to all that visit and study the monastery, and even to the ones that study its impact in the Portuguese sculptorical art, a better and global comprehension of the Portuguese religious scenography of the barroc period and the importance of local resources in the development of the ceramic art.