Designing industrially scalable, green composite mats for the removal of terpenic resin: a comparative assessment of varnish cleaning performances and solvent ingress in paintings

Traditional methodologies used by restorers are based on applying a cotton swab soaked with solvents to clean the surface of an artwork and may bring about reduced integrity and authenticity. Moreover, substituting toxic organic solvents with greener alternatives is necessary to prevent negative health effects for the operators during restoration interventions, and it is crucial for the environment. The aim of this research is to propose a novel cleaning system through green, scalable composite materials saturated with greener solvents, avoiding cotton swabs, and to provide one-step cleaning carrying the cleaning agent on artwork in a controlled manner. Electrospinning technique is an effective way to produce fibers in the nanometer range, with tunable properties such as surface-to-volume ratio, porosity, morphology, and flexibility in surface functionalities. The formulated composites consist of recycled polyamide electrospun coupled with a cellulose-based bamboo or viscose non-woven absorbent layer. The composite mats were obtained by tuning the process parameters of the industrial electrospinning unit with the aim of upscaling. Recently developed polysaccharide-based pullulan electrospun mat and commercial Evolon® CR were also included for a comparative analysis of the removal of terpenic resin from an oil painting. The designed composite mats, pullulan electrospun mat, and Evolon® CR were extensively characterized through porometry, SEM, air permeability, tensile strength and flexural rigidity analysis. The solvent action which gives rise to pigment mobility was monitored using laser speckle imaging. The solvent ingress throughout the paint layers was examined by means of portable NMR-MOUSE (Nuclear Magnetic Resonance Mobile Universal Surface Explorer) analysis. This research was carried out within the framework of the European Union Horizon GoGreen project, which aims to develop remedial conservation techniques based on green principles. The formulated novel materials also intend to address the rising demand for greener cleaning approaches and provide new sources for the cultural heritage sector.