Extension study of the assessment of aqueous cleaning on nBA/MMA and EA/MMA acrylic paints

Abstract

Acrylic paints became popular among artists in the late 50′s. Some of the main conservation issues of these paints are inherent to their composition characteristics, for instance, their high sensitivity to water and a wide range of polar solvents. This makes difficult to stablish an accurate and respectful cleaning treatment for this kind of artworks. As reported on previous studies, the application of pH and conductivity adjusted solutions using accurate methods, such as confined on chemical gels, improved this kind of procedures.The aim of this work is to extend a previous study where the effect of water based cleaning treatments was tested on Liquitex acrylic paint mock-ups, and deepen on evaluating the alterations both on the surface and in the bulk of the paint film. In this paper, six acrylic commercial paints of two widely used paint brands, Titan Arts – Acrílico extrafino (Spain) and Hyplar Acrylic Colors® (USA), were selected to compare the effect of the cleaning treatment on their surface and binder matrix. Samples were prepared using Mylar sheets and left to dry in a dark and dust-free environment for three years. Adjusted water solutions were applied both using cotton swab and cryogels for comparison. Paints were characterized using Fourier Transform Infrared spectroscopy (FT-IR), pyrolysis - gas chromatography - mass spectrometry (Py–GC–MS), Thermogravimetric Analysis (TGA) and Atomic Force Microscope (AFM).All the samples showed different reaction to cleaning according to their different composition. This study revealed that those paint films where most surface alterations are observed after cleaning, are not those that suffer greater changes in the binder matrix.Moreover, a set of samples was aged under accelerated conditions (solar radiation under controlled temperature and humidity). The accelerated ageing was carried out under isochronous sampling up to a maximum of 1426 h. This tests revealed certain degradation processes such as chain scission of the binder that coincide with those alterations observed in several mock-ups after application of the cleaning treatment.