Use of water - white spirit microemulsion to clean a white monochromatic painting by Gilda Azevedo

Abstract

Cleaning a painting is a process that requires knowledge of its materiality, integrity, and solvent systems. Aqueous solvent systems are a sustainable alternative, but their use must consider the potential harm that can arise in the process- such as swelling and leaching of layers underlying the dirt. Modern oil paintings made from the twentieth century onwards may be sensitive to aqueous solvents and suffer such damage. In this work, the cleaning of a white monochromatic oil painting by artist Gilda Azevedo was carried out with a microemulsified system of water in white-spirit using Tween 80 and ethanol as surfactant and cosurfactant, respectively. The microemulsified system and emulsions are the result of a ternary pseudodiagram where water, white-spirit, and surfactant/cosurfactant are carefully rationed. The emulsions obtained were characterized by measurements of conductivity and Dynamic Light Scattering. The artwork was examined by infrared absorption spectroscopy and X-ray fluorescence spectroscopy. Cleaning tests were firstly performed with emulsions and microemulsion and the removal of pigments was qualitatively analyzed by X-ray fluorescence spectroscopy. It was observed that the microemulsified system was an efficient cleaner while causing less removal of pigments compared to emulsified systems and, thus, chosen for cleaning. This cleaning efficiency was attributed to the use of water-white-spirit mixes capable of interacting with hydrophobic and hydrophilic substances in dirt. The lower pigment removal was ascribed to the dynamic percolation system and the nanometric size of the microemulsions.