Hermans Joen, Zuidgeest Lonneke, Iedema Piet, Woutersen Sander, Keune Katrien
Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD Amsterdam, The Netherlands.
Conservation & Science, Rijksmuseum, PO Box 74888, 1070DN Amsterdam, The Netherlands.
Phys Chem Chem Phys. 2021 Oct 13;23(39):22589-22600. doi: 10.1039/d1cp03479k.
The crystallization of metal soaps in oil paint is an important chemical phenomenon that affects the appearance and structural stability of many works of art. A deep understanding of the structural transitions that occur during crystallization and their kinetics will help to support conservation decisions that minimize future detrimental change to paintings. We have used a method based on attenuated total reflection Fourier transform infrared spectroscopy and detailed spectrum analysis to quantitatively monitor all relevant metal soap structures during crystallization in a linseed oil matrix with varying degrees of polymerization. It was found that zinc soap crystallization behaviour is strongly influenced by the properties of the oil matrix, slowing down drastically with increasing polymerization, forming crystalline polymorphs in varying ratios, and demonstrating two-stage kinetics. In contrast, lead soap crystallization was invariably fast, but the degree of disorder in the crystallized phases was increasing with matrix polymerization. Besides fundamental insight into the mechanisms of metal soap crystallization, the results lay foundations for improved risk assessment during conservation treatment of oil paintings.
金属皂在油画中的结晶是一种重要的化学现象，它会影响许多艺术品的外观和结构稳定性。深入了解结晶过程中发生的结构转变及其动力学，将有助于做出保护决策，尽量减少未来对绘画作品的有害变化。我们采用了一种基于衰减全反射傅里叶变换红外光谱法和详细光谱分析的方法，来定量监测在具有不同聚合度的亚麻籽油基质中结晶过程中所有相关金属皂结构。研究发现，锌皂的结晶行为受油基质性质的强烈影响，随着聚合度的增加结晶速度大幅减慢，形成不同比例的结晶多晶型物，并呈现出两阶段动力学。相比之下，铅皂的结晶总是很快，但结晶相中的无序程度随着基质聚合度的增加而增加。除了对金属皂结晶机制有基本的认识外，这些结果还为改进油画保护处理过程中的风险评估奠定了基础。
