A COMPARATIVE MULTI-TECHNIQUE INVESTIGATION ON MATERIAL IDENTIFICATION OF GILDING LAYERS AND THE CONSERVATION STATE OF 7 PORTUGUESE MANNERIST ALTARPIECES

Abstract

This paper deals with the multi-analytical comparative characterization of 59 samples of gilded and polychrome layers from 7 altarpieces studied during the Gilt-Teller project (www.gilt-teller.pt). The altarpieces studied here belong to seven churches in the areas of Lisbon, Santarém, Portalegre and Guarda and display stylistic and constructive features characteristic to the Mannerism carved wood decoration in Portugal. The applied protocol of investigation characterized the structure and manufacture technique of gilding; identified the chemical composition of the layers constituting the gilded polychrome decoration; compared the materials and gilding techniques encountered in the 7 altarpieces and assessed the conservation state of each altarpiece. The analytical techniques applied to these purposes were: stereomicroscopy (SM), optical microscopy (OM), scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX), X-ray diffraction (XRD), MALDI-TOF mass spectrometry, μRaman and μFTIR/imaging μFTIR spectroscopies. This interdisciplinary multi-scale approach was used to elucidate the aspects related to the material and technical aspects of “talha dourada” decoration, answering to these questions: which are the original materials and layers in the making of the polychromy and which are the ones added with posterior interventions; which are the relationships between gilding materials and techniques, regarding the degree of erudition of each case study; which were the main causes of degradation and influence to their conservation condition