The effects of strain rate and temperature on commercial acrylic artist paints aged one year to decades

Acrylic artist paints are viscoelastic composites containing a high molecular weight copolymer, pigment and a variety of additives. The glass transition temperature of the latex binder is typically slightly below ambient conditions, giving mechanical properties that are strongly dependent on strain rate and temperature. In previous work, the viscoelastic behaviour of custom-formulated latex artist paints was reported for films with known volume fractions of pigment using data from uniaxial tensile tests at different strain rates and temperatures. Secant Young’s modulus and failure strain master curves were constructed for each film through time-temperature superposition, allowing predictions beyond the experimental timescale at a selected reference temperature. A similar analysis is now presented for a small set of commercial artist paints tested at ages of 1 and 27 years. Experimental shift factor values are reported with fits to the Arrhenius, WLF and Vogel Fulcher equations, along with a comparison with published data for acrylic polymers. The tensile results highlight a spectrum of properties that acrylic paints may exhibit—brittle glass to hyperelastic—depending on the conditions during deformation. Strong similarities are shown between products from different manufacturers, and the findings suggest a high degree of stability with age. A method for predicting failure as a function of strain rate and temperature is also presented, and the methodology gives a framework for investigating other artist materials and the factors influencing their mechanical properties

Spectroscopic techniques and the conservation of artists’ acrylic emulsion paints

Artists’ acrylic emulsion paints are used in many contexts such as paintings, murals, sculptures, works on paper and mixed media; and are forming increasing proportions of modern and contemporary art collections. Although acrylic emulsion paints have been the focus of museum-led research over the past decade, the impact of artists’ technique and conservation treatment on the upper-most surface of these paints remains essentially unexplored ; This paper summarises previous studies using vibrational (FTIR) spectroscopy and presents initial assessments of paint surfaces using X-ray spectroscopies (XPS and NEXAFS) aimed at characterising artists’ acrylic paint film surfaces after natural ageing and wet surface cleaning treatment. Both techniques were found to be well suited for surface-sensitive investigations of the organic materials associated with artists’ acrylic paints, including explorations into: (A) cleaning system residues, (B) surfactant extraction from paint surfaces, (C) the identification of migrated surfactant, and (D) monitoring pigment changes at the paint/air interface of paint films ; It has been shown is that these X-ray spectroscopic techniques can be used for the analysis of almost purely organic materials in a way that complements mass spectroscopic techniques, FTIR and XRF. This investigation forms part of broader, currently ongoing, multi-technique investigation into the properties of artists’ acrylic paints and development of conservation treatments for works-of-art made with these materials

Evaluation of a gelatin-based adhesive for historic paintings that incorporates citronella oil as an eco-friendly biocide

[EN] The presented study focuses on evaluating the efficiency of a gelatin-based product that incorporates a plasticizer (glycerol) and a biocide (citronella oil), proposed as an eco-friendly adhesive for polychrome decoration applied in different parts of the architectural complex of the Longshan Temple in Lukang (eighteenth century, Taiwan). Seven laboratory physico-chemical tests were performed: (a) viscosity measurement; (b) drying curves; (c) moisture content determination; (d) water vapor permeability test; (e) mechanical test; (f) adhesion test; (g) susceptibility to fungi colonization test, which provide information on the workability, water content and water barrier properties, as well as mechanical, adhesion, and the biocide properties of the proposed product. The obtained results indicate that the workability, mechanical and adhesive properties of the new adhesive are adequate. Permeability in polychromies is slightly reduced due to the additional barrier effect of the adhesive incorporated into the paint film. The efficiency of citronella oil for preventing the growth of fungus Aspergillus niger on paintings consolidated with the adhesive was also probed. In parallel to these laboratory trials, the micro-invasive tests carried out, using nanoindentation combined with atomic force microscopy (NI-AFM), provided direct evidence for the improvement in the mechanical properties induced by applying the new adhesive to the original polychromies.This work was supported by the Spanish Ministerio de Economia, Industria y Competitividad (MINECO), the Fondo Europeo de Desarrollo Regional (ERDF), and the Agencia Estatal de Investigacion (AEI).Lee, Y.; Martín Rey, S.; Osete Cortina, L.; Martín-Sánchez, I.; Domenech Carbo, MT.; Bolivar-Galiano, F. (2018). Evaluation of a gelatin-based adhesive for historic paintings that incorporates citronella oil as an eco-friendly biocide. Journal of Adhesion Science and Technology. 32(21):2320-2349. https://doi.org/10.1080/01694243.2018.1477411S23202349322

Study of behaviour on simulated daylight ageing of artists¿ acrylic and poly(vinyl acetate) paint films

[EN] This work proposes a multi-method approach that combines advanced microscopy (SEM/EDX, AFM) and spectroscopy (UV-vis and FTIR) techniques. This approach not only characterises the behaviour of the additives of two commercial poly(vinyl acetate) (PVAc) and acrylic emulsion paints but also simultaneously characterises the changes in chemical composition and morphology observed in the paint films as a result of ageing due to the paints being exposed to an intense source of simulated daylight. In parallel, a series of mechanical tests were performed that correlate the chemical changes in composition and the changes observed in the films' mechanical properties. This work was a comparative study between both types of acrylic and PVAc paints. The results obtained are of great interest for the modern paint conservation field as they provide valuable information on the mid- and long-term behaviours of these synthetic paints.Financial support is gratefully acknowledged from the Spanish "I+D+I MICINN" project CTQ2008-06727-C03-01/BQU supported by ERDEF funds and from the "Generalitat Valenciana" I+D project ACOMP/2009/171 and the AP2006-3223 project ascribed to the Predoctoral Stages Programme of Universitary Researchers in Spanish Universities and Research Centres from the Spanish Ministry of Science and Innovation (MICINN). The authors wish to thank Mr. Manuel Planes i Insausti and Dr. Jose Luis Moya Lopez, the technical supervisors responsible for the Electron Microscopy Service at the Polytechnic University of Valencia.Domenech Carbo, MT.; Silva, MF.; Aura Castro, E.; Fuster López, L.; Kröner ., SU.; Martínez Bazán, ML.; Mas Barberà, X.... (2011). Study of behaviour on simulated daylight ageing of artists¿ acrylic and poly(vinyl acetate) paint films. Analytical and Bioanalytical Chemistry. 399:2921-2937. https://doi.org/10.1007/s00216-010-4294-3S2921293739

Anselm Kiefer: a study of his artistic materials

The style of the contemporary German artist Anselm Kiefer is highly innovative and unconventional and is characterized by the use of diverse materials that he selects and combines according to the emotions that they stir in him. The conservation and preservation of works by Kiefer are particularly difficult tasks because of the heterogeneity and, in some cases, the incompatibility of the materials used; therefore, a thorough characterization is crucial before any intervention is considered. In this paper, we report the results of an investigation on a fragment from a multimaterial work and on samples from the paintings Bohemia Lies by the Sea and Die Größe Fracht. The large fragment was cut by the artist himself from a work in progress and is considered destitute of any artistic value; therefore, it was possible to sample it extensively. This fragment and the samples from the Die Größe Fracht and Bohemia Lies by the Sea paintings were analyzed by ultraviolet (UV) fluorescence imaging, fiber optic reflectance spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance, Raman spectroscopy, X-ray diffraction, gas chromatography-mass spectrometry, and pyrolysis gas chromatography-mass spectrometry. This multitechnique approach allowed us to fully characterize and identify pigments, dyes, and organic components that reflect the diversity of the materials typically chosen by the artist. The results are evaluated in the context of the interview that Antonio Rava had with the Anselm Kiefer in 2000