Multi-approach study applied to restoration monitoring of a 16th century wooden paste sculpture

A multi-approach study has been designed to evaluate the mannerist-style masterpiece of the Christ of the Expiration (Museum Brotherhood, Seville, Spain), a polychrome wooden paste sculpture of the 16th Century that was restored in the Andalusian Historical Heritage Institute (IAPH). During its intervention, a combination of two non-destructive prototypes were used to evaluate the different color in its feet regarding its legs and torso and its cause. A portable equipment that combined X-ray diffraction (XRD) and X-ray fluorescence (XRF) was employed to analyze chemical composition and mineralogical characterization of pigments. This equipment allowed obtaining simultaneously XRF and XRD at the same point without sampling. X-ray techniques identified cerussite, hydrocerussite and barite in different layers. The presence of zinc oxide from a recent restoration was also detected. Additionally, laser induced fluorescence (LIF) was employed to assess the presence of different fluorescent compounds on the surface. This technique showed the use of acrylic products in the feet, loincloth and torso of Christ from previous restoration and allowed to detect spectral difference on the feet and a high ration of the acrylic product on feet, both could be the cause of the differential degradation between the feet and torso. This multi-approach study based on portable and non-destructive techniques allowed restoration monitoring and helped restorers to take decisions without sampling.