Characterization of morphological and chemical changes at micro- and nano- scale in contemporary paintings treated with biocides

Annette S. ORTIZ MIRANDA / María Teresa DOMÉNECH-CARBÓ / Antonio DOMÉNECH
(Instituto de Restauración, Universitat Politècnica de València, Spain)

Keywords: biocide, acrylic paints, PVAc paints

Abstract:
The growing problems of biodeterioration undergone by commercial artists’ paints have increasingly required the application of biocide treatments on contemporary artworks. In most cases, commercial biocides, which have not been created for the purpose of being used in the field of art conservation, are applied in the dosages recommended by the manufacturer without control on the effects of their application on the artwork. From this, a study has been conducted aimed to evaluate the changes induced by the biocide on contemporary paintings of acrylic and PVAc type. Two biocides have been considered, namely, Biotin T® and Preventol RI80®. Chemical changes have been identified by using FTIR spectroscopy and UV-VIS spectrophotometry. The morphological study at microscale has been performed by using optical microscopy and SEM-EDX. In a second step chemical and morphological changes at nanoscale have been characterized by using, at first time in the field of the analysis of artworks, the novel technique of electrochemical atomic force microscopy (ECAFM). Some of the most significant changes observed by microscopy were: appearance of spots and alteration of the brightness of the paint film, as well as, deposits of biocide. A notable delay in the coalescence phase of drying of the acrylic polymer used as binding media was recognized by means of ECAFM. Spectroscopic analysis results suggest that the application of the biocide causes a significant migration of additives to the surface from the core film. Acknowledgements.- Financial support is thanked to the Spanish (MICINN)  R+D Project CTQ2011-28079-C03-01 and 02  also supported with ERDF funds. Research was conducted within the “Grupo de análisis científico de bienes culturales y patrimoniales y estudios de ciencia de la conservación” Microcluster of the University of Valencia Excellence Campus (Ref. 1362).