Shrinkage and mechanical properties of drying oil paints

Heritage Science

卷:10

Research

Marion F. Mecklenburg¹  Damien Favier²  Patrick Kékicheff²  Arkadiusz Janas³  Łukasz Bratasz³  Roman Kozłowski³  Mikkel Scharff⁴  Cecil Krarup Andersen⁴  Laura Fuster-López⁵ 

[1] Formerly Senior Research Scientist, the Smithsonian Museum Conservation Institute, Washington, USA;

[2] Institut Charles Sadron, Université de Strasbourg, CNRS-UPR22, 67034, Strasbourg, France;

[3] Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30-239, Kraków, Poland;

[4] The Royal Danish Academy, Conservation, Philip de Langes Allé 10, 1435, Copenhagen K, Denmark;

[5] Universitat Politècnica de València, Instituto Universitario de Restauración del Patrimonio, 46022, Valencia, Spain;

关键词: Oil paints;    Drying;    Mechanical properties;    Shrinkage;    Cracking;    Paintings;   

DOI  :  10.1186/s40494-022-00814-2

 received in 2022-07-12, accepted in 2022-10-08,  发布年份 2022

来源: Springer

【 摘 要 】

Understanding how the evolving molecular composition of an oil paint layer on its transition to an aged solid film affects its dimensional change and mechanical properties is fundamental to the assessment of material durability and more broadly risk of degradation of oil paintings. Tensile properties—modulus of elasticity and strain at break—as well as cumulative shrinkage were determined for a selection of oil paints from Mecklenburg’s Paint Reference Collection now after approximately 30 years of drying. The oil paints were found to get stiffer and more brittle with diminishing plastic deformation and increasingly elastic behaviour. For some paints, the increases in stiffness and decreases in the strain at break were dramatic during the late stage of drying. The observations modify the current physical model of paintings in which the mismatch in the response of glue-based ground layer and unrestrained wood or canvas support to variations in relative humidity (RH) has been identified as the worst-case condition for the fracturing of the entire pictorial layer. This study demonstrated that some paints were more brittle than the glue-based ground layer and as a consequence more vulnerable to cracking. The shrinkage of paints due to molecular relocation and/or evaporation of organic medium as they dry and age was measured. This shrinkage can exceed their strain at break and lead to fracturing of the oil paint layer if it is restrained by a dimensionally stable substrate. Consequently, after long-term drying, the cumulative shrinkage can cause oil paints to crack even in absence of fluctuations in RH or temperature. An example of cracking developed in an oil paint layer on the top of an undamaged ground layer in a historic panel painting was made evident by the X-ray microtomography.

【 授权许可】

CC BY   
© The Author(s) 2022

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