Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
Appl Spectrosc. 2010 May;64(5):528-36. doi: 10.1366/000370210791211628.
The application of laser cleaning methodologies to light-sensitive substrates such as those encountered in artistic paintings is an extremely delicate issue. The cleaning of paintings and polychromes is an irreversibly invasive intervention; therefore, prior to the implementation of laser cleaning methodologies, a thorough characterization of the interaction between laser pulses and painting components is required. In this work, the modifications induced by irradiation with pulses of 150 picoseconds (at 1064 and 213 nm) and 15 nanoseconds (at 213 nm) on unvarnished aged model egg-yolk-based paints were examined following a spectroanalytical approach. Laser-induced chemical changes on samples of unpigmented and widely used artist's pigment temperas were investigated by spectrofluorimetry and Fourier transform Raman spectroscopy, while color changes were quantified by colorimetry. Noticeable modifications of the Raman and fluorescence bands attributed to pigments are absent except for vermillion, for which the pigment bands tend to disappear upon irradiation at 1064 nm. Interestingly, no discoloration was observed on most of the pigments upon irradiation at 213 nm (150 ps), including the light-sensitive vermillion, while no indications of carbonization or charring of the paint layers, which could give rise to amorphous carbon bands, were obtained at any of the irradiation conditions explored. Comparison of the results using the two different pulse durations and wavelengths illustrates the participation of mechanisms of diverse origin according to the chemical composition of the pigment and highlights the importance of the optimization of the laser parameters, specifically fluence, pulse duration, and wavelength, in conservation treatments of paintings.
将激光清洁方法应用于光敏感基底，如艺术画作，是一个极其微妙的问题。绘画和多彩画的清洁是一种不可逆的侵入性干预；因此，在实施激光清洁方法之前，需要对激光脉冲与绘画成分之间的相互作用进行彻底的特征描述。在这项工作中，通过光谱分析方法研究了未上光的老化模型蛋黄基涂料在 150 皮秒（1064nm 和 213nm）和 15 纳秒（213nm）脉冲辐照下引起的变化。通过光谱荧光法和傅里叶变换拉曼光谱研究了未着色和广泛使用的艺术家颜料蛋彩画样品的激光诱导化学变化，而颜色变化则通过比色法进行量化。除朱红色外，除了朱红色外，没有观察到归因于颜料的拉曼和荧光带的明显变化，因为在 1064nm 辐照下，颜料带趋于消失。有趣的是，在 213nm（150ps）辐照下，大多数颜料都没有变色，包括光敏感的朱红色，而在任何所探索的辐照条件下，都没有观察到颜料层碳化或烧焦的迹象，这可能会产生无定形碳带。使用两种不同的脉冲持续时间和波长比较结果说明了根据颜料的化学成分参与了不同来源的机制，并强调了优化激光参数（特别是能量密度、脉冲持续时间和波长）在绘画保护处理中的重要性。
