Cleaning acrylic paints: mineral spirits-based microemulsions and the question of residues

This paper presents a summary of some research into the evaluation of mineral spirits-based microemulsions as wet surface cleaning systems for artists’ acrylic emulsion paint films. Examples from four different mineral spirits-based microemulsion systems were evaluated, each having a different primary surfactant component. Particular attention is given here to determination, using surface-sensitive analytical techniques (ATR-FTIR, XPS and ToF-SIMS), of possible microemulsion surfactant residues remaining on paint films after wet cleaning treatment. Three different test paint films were subjected to simulated cleaning treatments: Golden Heavy Body Acrylic PY3 (azo yellow); Liquitex Heavy Body Artist Acrylic PY3 (azo yellow); and Liquitex Heavy Body Artist Acrylic PW6 (titanium white). In comparison with untreated controls, samples were analysed by the above methods at two stages: after treatment with cleaning liquid but without any clearance step, and again after clearance of any residue with hydrocarbon solvent. These investigations have shown that only trace amounts of surfactant residues may remain on paint surfaces. Indications of the presence of residual surfactant naturally depends on the respective sensitivities of the different analytical techniques: the detection limit for ATR-FTIR is lower than XPS and ToF-SIMS. As has been shown to be the case for aqueous treatments, levels of intrinsic surfactant in acrylic paint films and migrated surfactant located at paint surfaces can also be affected by these cleaning treatments.