Non-invasive reflection FT-IR spectroscopy for on-site detection of cleaning system residues on polychrome surfaces

In the present study, we propose reflection FT-IR spectroscopy as non-invasive tool for monitoring cleaning residues from polychrome surfaces. Tests on simplified model paints allowed defining the analytical strengths both in term of selectivity and detection limits towards thickeners, surfactants and chelating agents most commonly used in cleaning formulations. Subsequently, the detection of these components has been assessed on aged paint mock-ups and an easel painting after cleaning with different gel formulations. The obtained results clearly proved the strengths of reflection FT-IR spectroscopy for a real time, non-invasive detection of cleaning residues on polychrome surfaces. Thickeners such as Klucel (R) G, surfactants including Ethomeen (R) C/12 and C/25 and chelating agents (citric acid + TEA, tetrasodium EDTA salt) were clearly detected after dry removal of the gels and in some tests also after the clearance step.