Fourier transform infrared spectroscopy and the analytical study of works of art for purposes of diagnosis and conservation

This paper is a study of the analytical capacity of Fourier transform infrared spectroscopy (FT-IR) for any type of samples from works of art. The analytical information obtained with this technique on organic and inorganic compounds is extremely useful in the preliminary studies necessary for diagnosis and to decide on the conservation process. This paper reports the analysis and study with FT-IR on samples extracted from the microlayers in several works of art from different periods (16th to 18th century) comprising wall paintings and canvas. The most outstanding of these being the frescoes by A. Palomino from two ceilings in the Santos Juanes church. The analytical procedures for the different components of the works studied such as

1. (a) varnish applied to wood panels and canvas paintings,

2. (b) binding media and pigments used by the artists,

3. (c) inerts, mortars, stuccos and grounds have been optimized. The FT-IR technique offers a quick analysis of microsamples (less than 0.5 mg) and is able to characterise the different molecular groups which provide information on the nature of the different materials of organic and inorganic origin used by the artist and thus permits the diagnosis of pathologies requiring conservation treatment.

How mobile NMR can help with the conservation of paintings

The conservation of paintings is fundamental to ensure that future generations will have access to the ideas of the grand masters who created these art pieces. Many factors, such as humidity, temperature, light, and pollutants, pose a risk to the conservation of paintings. To help with painting conservation, it is essential to be able to noninvasively study how these factors affect paintings and to develop methods to investigate their effects on painting degradation. Hence, the use of mobile nuclear magnetic resonance (NMR) as a method of investigation of paintings is gaining increased attention in the world of Heritage Science. In this mini-review, we discuss how this method was used to better understand the stratigraphy of paintings and the effect different factors have on the painting integrity, to analyze the different cleaning techniques suitable for painting conservation, and to show how mobile NMR can be used to identify forgeries. It is also important to keep in mind its limitations and build upon this information to optimize it to extend its applicability to the study of paintings and other precious objects of cultural heritage.     

颜料层微观形貌对古代壁画褪色及显现影响

文物壁画在自然环境下产生褪色现象具有复杂性,严格意义上讲,人们无法重现自然环境下这种褪色发生的条件,但这并不妨碍人们研究其褪色原因的可能性和途径。通过实验来验证所提出机制的合理性,这也符合自然科学普遍采用的研究方法。提出颜料层微观形貌变化是引起壁画褪色的一种重要原因。胶料作为颜料层的连续相,当胶料分解时,颜料层微观形貌必然产生变化,为证明这种变化会引起颜料层褪色,而非颜料变化所致。建立了以具有较高热稳定性的赭石为颜料,以明胶作为粘接剂制成模拟的壁画颜料层。然后通过加热处理使胶料发生氧化分解,从而造成颜料层微观形貌发生变化,但赭石颜料依然稳定,期望证明在颜料赭石不发生变化时,由于颜料层微观形貌变化也可引起颜料褪色。实验通过煅烧壁画颜料层模拟样获得胶料降解的壁画模型,分别以SEM及多角度反射率光谱等技术,考察模拟样胶料降解前后表面微观形貌和光学性质变化。结果表明：壁画模拟样煅烧后,颜料层表面产生空隙结构,样品表面多角度反射率光谱表明煅烧后样品颜料层对可见光的反射增加而吸收降低,并观察到模拟样颜色淡化。以无色,难挥发,且不与颜料层发生化学反应的离子液体涂覆褪色样品表面,以上述技术表征涂覆处理前后颜料层表面微观形貌和表面光学性质变化,结果表明：离子液体填充了褪色样品表面颗粒间空隙,检测到样品表面对可见光的反射降低而吸收增加,观察到褪色样品的颜色加深。以上实验结果证明了推测合理性,即微观形貌变化确实会引起颜色变化。依据此原理以唐代墓室褪色壁画为例,进行了显现修复应用研究,其颜色显现效果显著。     

Design,Synthesis, and Phenotypic Profiling of Pyrano‐Furo‐Pyridone Pseudo Natural Products

Natural products (NPs) inspire the design and synthesis of novel biologically relevant chemical matter, for instance through biology‐oriented synthesis (BIOS). However, BIOS is limited by the partial coverage of NP‐like chemical space by the guiding NPs. The design and synthesis of “pseudo NPs” overcomes these limitations by combining NP‐inspired strategies with fragment‐based compound design through de novo combination of NP‐derived fragments to unprecedented compound classes not accessible through biosynthesis. We describe the development and biological evaluation of pyrano‐furo‐pyridone (PFP) pseudo NPs, which combine pyridone‐ and dihydropyran NP fragments in three isomeric arrangements. Cheminformatic analysis indicates that the PFPs reside in an area of NP‐like chemical space not covered by existing NPs but rather by drugs and related compounds. Phenotypic profiling in a target‐agnostic “cell painting” assay revealed that PFPs induce formation of reactive oxygen species and are structurally novel inhibitors of mitochondrial complex I.     

Pigment identification and decoration analysis of a 5th century Chinese lacquer painting screen: a micro‐Raman and FTIR study

To investigate the pigments and decoration applied to a wood‐based lacquer painting screen from the tomb of Si‐ma Jin‐long, Shanxi Province, central China, made by Chinese craftsmen in the 5th century, a combination of micro‐Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), wavelength dispersive X‐ray fluorescence (WDXRF), and microscopic examination was used. The obtained results are as follows: (1) the black, yellow, and red colors are identified as carbon black, orpiment and realgar, and cinnabar, respectively, by using micro‐Raman spectroscopy. The FTIR result shows that the white pigment filled in the leaves is not lead white, as assumed in the literature, but gypsum. Whether lead white was used at other locations remains unanswered and requires more samples for further work; (2) the thickness of each discernable pigment layer, as observed under the microscope, is approximately equal and the differences among them are small, suggesting a superfine painting skill; besides, a noticeable smooth interface between wood and the red grounding substance indicates that a polishing process might have been applied before the painting; (3) the red background was proved to contain cinnabar, but further FTIR analyses found no evidence for the presence of Chinese wood oil; and (4) the most interesting finding, rarely reported before, is that white grains of different sizes are found in both pigment layers and the grounding substance, which are perhaps an intentional addition. Further, in situ XRF and Raman analyses indicate that they are sourced from hydroxyapatite, coming probably from the intentional addition of animal bone ash to the lacquer. But how such a process could be finished and what purpose it served have not yet been answered. Copyright © 2009 John Wiley & Sons, Ltd.     

目标红外迷彩伪装技术研究

随着红外迷彩伪装涂料的出现,利用其对目标红外热图像进行分割,破坏目标图像特征的特点,为目标红外对抗提供了一种新的有效手段.首先,以传热模型为基础,模拟出目标的表面温度,并通过实测得出背景的表面瞬态温度.然后,利用随机生成的方法,生成背景的红外纹理图像.最后,以目标与背景的辐射对比度为基础,对红外迷彩涂料的设计参数进行了优化,分析了红外迷彩涂料的设计参数和图案设计对目标伪装效果的影响,达到了较好的红外伪装效果.     

Scientific investigations of the Imperial Gates from the Petrindu wooden church,Salaj County,Romania

In order to preserve and restore the Imperial Gates from the Petrindu wooden church, Salaj County, Romania, (map location—latitude, longitude: 46.97, 23.19), the scientific investigation of the wooden support and painting materials (ground and pigments) was performed, employing Fourier‐transform infrared spectroscopy (FTIR), X‐ray fluorescence spectroscopy, and 3D scanning. FTIR spectroscopy offered information about the wooden degradation stage, whereas X‐ray fluorescence and FTIR spectroscopic methods were employed for structural painting materials characterization. The structural data can be correlated with the artistic, theological, and historical analysis of this religious patrimony object. After obtaining information about the wooden support and painting materials, the Imperial Gates were 3D digitized using state of the art laser scanning technology. The digital 3D model obtained was restored in a virtual environment and converted into an interactive 3D model that can be used for Romanian cultural heritage digital dissemination.     

基于可见光谱的古代壁画颜料无损鉴别方法

矿物颜料是古代壁画显色的物质基础,其可见光谱反映自身物质和物理属性。不同颜料对可见光吸收特性的差异导致光谱曲线形状不同,同一种颜料因粒径等级差异引起光谱曲线幅值的规律性变化。依据矿物颜料上述特性,提出一种基于可见光谱的古代壁画颜料无损鉴别方法,通过光谱归一化方法实现不同粒径等级的同一颜料光谱曲线叠合,去除颜料粒径等级对光谱曲线幅值变化的影响,然后提取表征光谱曲线在各波段增减性和凹凸性的一阶与二阶导数特征,与光谱曲线组合得到颜料物质属性鉴别的光谱组合特征空间,以光谱角和欧式距离为基础构建评价指标,计算待鉴别颜料与数据库参考样本在光谱特征空间中的匹配误差(ME),实现颜料物质属性的鉴别。通过构建矿物颜料平均粒径大小和光谱反射率均值之间关系函数,实现颜料平均粒径大小的鉴别。基于构建的古代壁画常用颜料光谱数据库,以莫高窟壁画为对象,通过非接触式原位无损测量方法测量获得壁画颜料的可见光谱数据,对本文方法进行了验证,并以石绿和青金石颜料的鉴别结果为例,对古代壁画颜料使用技法、不同朝代颜料使用的差异性及原因进行了探讨。该方法将为更加全面深入研究和保护古代壁画提供有效的理论与方法支撑。     

In situ investigation of synchrotron radiation damage effect of ancient paintings by time-resolved ED-XAS and IR combined techniques

Advanced synchrotron radiation light is a powerful tool for archaeometry research. However, its applications to precious cultural relics, especially for color painting, have been hindered to some degree due to potential X-ray radiation damage. Compared to inorganic mineral pigments, organic binders in the painting are easier to be damaged by synchrotron radiation X-ray beam. The radiation damage effect of two typical painting samples, pure rabbit skin glue and the mixed sample of rabbit skin glue and zinc white, has been investigated by in situ time-resolved ED-XAS and IR combined techniques. The results show that the radiation damage effect of pure rabbit skin glue is more serious at low X-ray energy (7775 eV). The radiation damage effect of the mixed sample increases significantly due to more X-ray absorption by inorganic pigments. Furthermore, the radiation damage is more serious at the energy near Zn K-edge and is somewhat slight at higher energy (13,054 eV). These damages are more obvious from the point of view of protein secondary structures. The irradiation damage effects increase more rapidly at the beginning and are not linear with the irradiating time. The results indicate that synchrotron radiation damage can be reduced effectively by using X-ray energy far away from the X-ray absorption edge of the major element in the pigments during XRF, XRD and CT experiments, or by using time-resolved techniques such as QXAFS and ED-XAS during XAFS experiments.