Twin-chain polymer networks loaded with nanostructured fluids for the selective removal of a non-original varnish from Picasso\u2019s \u201cL\u2019Atelier\u201d at the Peggy Guggenheim Collection, Venice

Luciano Pensabene Buemi,Rodorico Giorgi,Piero Baglioni,David Chelazzi,Maria Laura Petruzzellis,Michele Baglioni,Rosangela Mastrangelo

doi:10.1186/s40494-020-00420-0

Abstract

This paper reports on the evaluation of a polyvinyl alcohol (PVA) “twin-chain” polymer network (TC-PN) combined with an oil-in-water nanostructured fluid (NSF) for the removal of a polyvinyl acetate (PVAc) varnish. Small Angle X-ray Scattering, Confocal Laser Scanning Microscopy, and Fluorescence Correlation Spectroscopy showed that the structure of the gel and the NSF are only minimally altered by loading the fluid into the gel. The NSF is partially free to diffuse through the network, but also interacts with the gel walls. During the cleaning, the dynamics of the fluid at the gel-substrate interface are controlled by the osmotic balance taking place among the interconnected pores. These features grant effective and controlled cleaning performances. The case study identified for this research is Pablo Picasso’s The Studio (L’Atelier, 1928), one of the masterpieces in the Peggy Guggenheim Collection, Venice (PGC). In 1969 the oil painting, originally unprotected, was wax-lined and then varnished using a PVAc varnish. Over the years, the white shades of the painting have been compromised by the yellowing of the varnish and soiling of deposits. On painting mock-ups, the NSF-loaded hydrogels allowed the swelling and softening of PVAc varnish and wax layers, which were then removed with gentle mechanical action. Effective varnish and wax removal at the micron scale, and the absence of residues from the cleaning system (gel and NSF), were confirmed by Fourier Transform Infrared Spectroscopy (FTIR) 2D imaging. The effective and safe removal of the aged PVAc varnish and wax layer from the surface of the painting was then carried out using the same cleaning protocol successfully tested on the mock-ups, setting the NSF-loaded PVA TC-PNs as robust and reliable tools for the cleaning of sensitive works of art.

Highlights

Over the last three decades, research increased our knowledge of the chemical, physical and mechanical properties of modern paints, and of their behavior and Pensabene Buemi et al Herit Sci (2020) 8:77 theoretical, scientific and practical in-depth study
The teamwork by conservators and scientists and their careful assessment allowed the validation of polyvinyl alcohol (PVA)-based hydrogels, made of polymer chains combined with PVA of lower molecular weight, which were developed at the Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI)
This paper reports on the evaluation of a PVA twin-chain” polymer network (TC-PN) formulated to be combined with an oil-in-water (o/w) nanostructured fluid (NSF), and targeted to the removal of a polyvinyl acetate (PVAc) non-original varnish from the oil painting The Studio by Picasso

Summary

Introduction

Over the last three decades, research increased our knowledge of the chemical, physical and mechanical properties of modern paints, and of their behavior and Pensabene Buemi et al Herit Sci (2020) 8:77 theoretical, scientific and practical in-depth study. The 3-year project involved selected case studies from the collection of the PGC: Jackson Pollock, Two (1943–45), and Eyes in the Heat (1946–47); Pablo Picasso, The Studio (1928); Giorgio de Chirico, The Gentle Afternoon (1916). These served as exemplary studies of the many conservation issues addressed by research, given the specific needs of each work of art. It was shown that the addition of the lower molecular weight PVA changes the porosity and mechanical properties of these gels as compared to single-PVA gels, and the cleaning efficacy is improved [1] These TC-PNs proved to be advantageous systems for the cleaning of paintings, owing to their mechanical properties, retentiveness, ability to remove soil, and the controlled cleaning process. The TC-PN used on the Pollock paintings had a tailored formulation in order to adapt to the specific requirements of those works, but served as a prototype for a series of multipurpose gels, which were formulated to target typical cleaning cases and named Nanorestore Peggy G els® and Nanorestore Peggy Gums®, after the PGC

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Conclusion