Mejía-González Adrián, Jáidar Yareli, Zetina Sandra, Aguilar-Rodríguez Pablo, Ruvalcaba-Sil J L, Esturau-Escofet Nuria
Instituto de Química, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Instituto de Investigaciones Estéticas, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Jun 5;274:121073. doi: 10.1016/j.saa.2022.121073. Epub 2022 Feb 24.
This study presents the use of high resolution Nuclear Magnetic Resonance (NMR) as an outstanding tool for identifying with accuracy the structure of the polymers used as binders and the additives used as plasticizers in samples from a mural painted by David Alfaro Siqueiros between 1964 and 1972, an important period in which his artistic production has not been previously studied. Additionally, the presence of some organic pigments was detected. The mural Trazos de composición piramidal currently located outside of Siqueiros' studio La Tallera, in Cuernavaca Morelos (Mexico) was an artistic experiment done by Siqueiros to test outdoor painting. Eight micro-samples of paint were thoroughly analyzed by Optical Microscopy (OM), Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fiber Optics Reflectance Spectra (FORS), Transmission Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance mode (FTIR-ATR) and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). Through these studies, contrasted with an historical investigation, we demonstrate that the samples present a multi-layered and complex painting system because Siqueiros made at least two versions of the painting. The multi-layered structure and the variable composition of each layer challenged the application of several analytical methodologies traditionally used for cultural heritage materials. In one sample, each layer was separated and they were studied in detail by FTIR-ATR, Py-GC/MS and NMR. This study revealed the presence of two main binders: acrylics in the first layers and nitrocellulose in the last one, also some phthalates and fatty acids were detected as additives. Inorganic pigments and fillers were identified as titanium dioxide and iron red oxide as well as diatoms and carbonates. The main contribution of this study, where NMR spectroscopy was applied for the first time in modern mural painting analysis, is the characterization of the materials used by Siqueiros during the last years of his artistic production.
本研究展示了高分辨率核磁共振（NMR）作为一种出色工具的应用，它能够准确识别1964年至1972年间大卫·阿尔法罗·西凯罗斯所绘壁画样本中用作粘合剂的聚合物结构以及用作增塑剂的添加剂结构，这是其艺术创作中一个此前未被研究过的重要时期。此外，还检测到了一些有机颜料的存在。目前位于墨西哥莫雷洛斯州库埃纳瓦卡西凯罗斯工作室“La Tallera”外的壁画《金字塔构图笔触》是西凯罗斯进行的一项户外绘画艺术实验。通过光学显微镜（OM）、扫描电子显微镜 - 能量色散X射线光谱仪（SEM - EDS）、光纤反射光谱（FORS）、衰减全反射模式的傅里叶变换红外光谱仪（FTIR - ATR）和热解气相色谱/质谱联用仪（Py - GC/MS）对八个油漆微样本进行了全面分析。通过这些研究，并与历史调查结果对比，我们证明这些样本呈现出一个多层且复杂的绘画体系，因为西凯罗斯至少绘制了两个版本的这幅画。多层结构以及每层的可变成分对传统用于文化遗产材料的几种分析方法的应用提出了挑战。在一个样本中，将每层分离，并通过FTIR - ATR、Py - GC/MS和NMR对其进行了详细研究。该研究揭示了两种主要粘合剂的存在：第一层为丙烯酸类，最后一层为硝化纤维素，还检测到一些邻苯二甲酸盐和脂肪酸作为添加剂。无机颜料和填料被鉴定为二氧化钛、氧化铁红以及硅藻和碳酸盐。本研究首次将NMR光谱应用于现代壁画分析，其主要贡献在于对西凯罗斯艺术创作后期所使用材料的表征。
