Abstract
This study concerns the assessment of a new polyvinyl alcohol–borax/agarose blend hydrogel (PVA–B/AG) tailored for the conservation of ancient Egyptian wall paintings. The increasing problems of deteriorated consolidants affecting ancient wall paintings have attracted the interest of conservation scientists in the last 20 years. The ability of a new blend for removing aged Paraloid® B-72 layers from painted stone and plaster samples has been evaluated. The hydrogel blend was used to expose the aged Paraloid in a controlled manner to six different cleaning system (CS). CS1–CS4 consist of solvents or solvent mixtures; CS5 and CS6 are nanostructured fluids (NSFs). The evaluation of the removal process was carried out by quantitative and qualitative methods, namely, visual examination, 3D microscopy, contact angle and colorimetric measurements and by Fourier transform infra-red spectrometry in reflectance mode. The results showed that the PVA–B/AG blend hydrogel, loaded with specific cleaning systems, was able to remove deteriorated B-72 and allowed to restore the painted surface to a state close to the original one. The PVA–B/AG blend showed good workability, permitting it to be easily cut, shaped, applied and removed. It could also be verified by means of different investigation methods that the blend left no detectable residues. As a final realistic check of the method, the PVA–B/AG hydrogel loaded with the best functioning cleaning system (CS3) was used to remove an aged consolidant layer from an ancient Egyptian wall painting.
Highlights
Wall paintings represent an important part of cultural heritage artefacts as they convey information on the life of our ancestors as well as their technologies
The decrease of the polymer/varnish layer thickness could be measured by optical coherence topography (OCT) or by means of a 3D microscope [51, 52]
The Polyvinyl alcohol (PVA)–B/AG blend hydrogel proved to be suitable for removing deteriorated Paraloid® B72 (B-72) from painted surfaces with different porosities
Summary
Wall paintings represent an important part of cultural heritage artefacts as they convey information on the life of our ancestors as well as their technologies. They are complex works of art because of their stratigraphy and variable inorganic and organic components [1, 2]. Over time, they are susceptible to degradation due to different external influences such as temperature, moisture, salts, light, micro-organisms etc. They are susceptible to degradation due to different external influences such as temperature, moisture, salts, light, micro-organisms etc On many archaeological surfaces that were treated, several drawbacks of their use have become apparent over the years: Al‐Emam et al Herit Sci (2019) 7:22
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