Experimentation of a PVA-Borax hydrogel for the removal of Paraloid B72® from artifacts of archaeological interest from the National Archaeological Museum in Naples, Italy

Abstract

This paper shows the results of an experimentation aimed at the removal of a polymeric film of aged Paraloid B72® originally placed to protect some wooden artifacts belonging to the Egyptian collection of the National Archaeological Museum of Naples (MANN). The study was conducted on two shabtis dated to the 19th Dynasty and a sculpture of Ptah-Sokar-Osiris dating to the late period. Thanks to the collaboration between the National Archaeological Museum of Naples and the Laboratory of Restoration of Wooden Artifacts of the University of Naples Suor Orsola Benincasa, it was possible to conduct an in-depth study of the artifacts, from both an archaeological-historical point of view and from a conservation point of view. This led to the development of the above-mentioned experimentation and to the planning of a proper restoration intervention. The study and experimentation were supported by several diagnostic techniques. In a first stage, non-invasive investigations were carried out to study the execution technique and the state of conservation of the artifacts. This allowed the recognition of the wood species that constituted the three sculptures through optical microscopy, whereas IR reflectography, UV induced fluorescence and X-ray radiation (XRF) were conducted to identify the type and the chemical nature of the pigments. Based on the above analysis, different restoration strategies, based on the removal of Paraloid B72® through a methodology that would act in full respect of the wooden support of the artifacts, were considered. Pros and cons of the different methodologies applied in the recent past for the removal of aged Paraloid from artifact surfaces were analysed. A removal technique based on the use PVA-Borax hydrogel loaded with a solvent mixture was selected. Experiments were conducted to validate the effectiveness of the selected method.