Abstract
Evolon^circledR CR is increasingly used in paintings conservation for varnish removal from oil paintings. Its key benefits over traditional cotton swabs are limiting solvent exposure and reducing mechanical action on the paint surface. However, this non-woven microfilament textile was not originally engineered for conservation use and little is known about its chemical stability towards organic solvents. Moreover, the physical processes of solvent loading and release by Evolon^circledR CR, as well as solvent retention inside paint after cleaning, have not been studied. These three topics were investigated using a multi-analytical approach, aiming for an improved understanding and optimized use of Evolon^circledR CR for varnish removal. Our results show that the tissue is generally chemically and physically stable to organic solvents when exposed on timescales that are typical in conservation practice. However, a pre-treatment step of Evolon^circledR CR is necessary to avoid the release of unwanted saturated fatty acids into the paint during varnish removal. We show that the primary mechanism of solvent uptake by the fibers is adsorption rather than absorption and that the dominant factor dictating the maximum solvent load is the volume of the voids between the fibers. Finally, solvent induced dynamics after application of solvent-loaded Evolon^circledR CR within the paint film was monitored using portable laser speckle imaging on model paints. A method to quantify solvent-retention in real-time was developed and revealed that the presence of varnish on paintings results in lower dynamics of solvents within the paint in comparison to unvarnished paint. Comparing various solvents, it was found that cleaning with acetone resulted in a roughly six-fold increase in dynamics compared to ethanol and isopropanol.
Highlights
The growing corpus of scientific literature dealing with the physicochemical aspects of oil paint alterations has led to concerns by conservators about unwanted adverse effects of solvents on paint films [1]
Benzoic acid (BZA) is used in the manufacture of caprolactam and terephthalic acid (TPA) [22], these fragments mainly originate from TPA fragmentation during pyrolysis [23]
As the paintings conservation field has rapidly discovered the potential of Evolon CR for varnish removal from oil paintings, the need to advance our understanding of this material and the steps necessary for safe and optimal usage increases
Summary
The growing corpus of scientific literature dealing with the physicochemical aspects of oil paint alterations has led to concerns by conservators about unwanted adverse effects of solvents on paint films [1]. Due to the limited knowledge regarding the short- and long-term chemical and physical stability of oil paintings, exposure of paint films to solvents should be kept to a minimum. To address these concerns, cleaning methods employing gels, gel composites or emulsions In the last 5 years, a new method of minimising solvent exposure has been developed using Evolon CR, a speciality-grade, non-woven microfiber cloth. This tissue is loaded/humidified with the conservator’s choice of. Manufactured by Freudenberg and marketed by Deffner & Johann, it is a blend of 70% polyester and 30% polyamide fibers spun into segmented filaments, and features a specific density of 77.4 g/m2 [16, 17]
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