Quantitative X-Ray Fluorescence Imaging to Evaluate the Efficacy of Micro-Structured Cellulose Foams and Poultices in Wall Painting Desalination

Abstract

The crystallization of soluble salts poses a significant challenge tomural painting conservation. While cellulose poultices are widelyused to desalinate mural paintings due to their high absorptionand ease of handling, their effectiveness within the porous networkof wall paintings remains a complex issue. For the first time,this study explores the potential of micro-structured cellulosebasedfoams as an alternative to conventional poultices for desalinatingfresco wall paintings. A laboratory experiment comparedthe efficacy of foams and poultices, using fresco wall paintingmock-ups (produced with the Roman technique) that were vacuum-impregnated with salt solutions (chlorides, sulfates, and mixtures).Short and long application times were considered, andfoam reusability across multiple application cycles was assessed.Micro-energy dispersive X-ray fluorescence (μ-EDXRF) imagingwas employed to quantitatively evaluate salt content reduction,both superficially and throughout the mock-up stratigraphy.Results show that foams are considerably more effective thanpoultices, achieving a salt removal efficiency between 6 and10 times higher. The uniform micro-porous foam network enablesfaster desalination, reducing treatment risks and minimizingwaste while supporting circular economy principles. This studyalso demonstrates the utility of μ-EDXRF imaging in monitoringdesalination efficacy for both surface and cross-section analyseswhen assessing new desalination protocols.