Centro di Eccellenza SMAArt (Scientific Methodologies applied to Archaeology and Art), c/o Dipartimento di Chimica, Università degli Studi di Perugia, Perugia, Italy.
Anal Bioanal Chem. 2013 Mar;405(8):2699-711. doi: 10.1007/s00216-013-6707-6. Epub 2013 Jan 23.
In this work non-invasive reflection infrared spectroscopy was used to discriminate between different Cu-based green pigments (namely, malachite, verdigris, chrysocolla, emerald green and phthalo green). The pigments, chosen because of their historical widespread use in artworks, were investigated as pure powders and in situ on painted models by reflection FTIR spectroscopy. The distortion arising as a result of the specular and diffuse component of reflected radiation was evaluated as function of the optical and surface properties of the investigated mock-ups. Use of the Kramers-Kronig (KK) algorithm to correct for the distortion arising from the surface reflection gave k index maxima shifted by more than 20 cm(-1) relative to those obtained in conventional transmission mode. These findings stress the need to carefully manage use of the KK algorithm on reflection spectra to avoid erroneous assignment. On the other hand, combination and overtone bands (which are enhanced by the diffuse reflection) were proved to enable reliable and sensitive identification of most of the pigments studied. Knowledge acquired by study of pure compounds and painted models was subsequently applied to interpret the spectra acquired from paintings and manuscripts.
在这项工作中，非侵入式反射红外光谱法被用于区分不同的铜基绿色颜料（即孔雀石、铜绿、硅孔雀石、翡翠绿和酞菁绿）。这些颜料因其在艺术品中的历史广泛应用而被选择进行研究，它们被作为纯粉末和原位在绘画模型上进行反射 FTIR 光谱研究。由于反射辐射的镜面和漫射分量而产生的失真作为所研究模型的光学和表面特性的函数进行评估。使用克朗尼格-克朗尼格（KK）算法来校正表面反射引起的失真，得到的 k 指数最大值相对于传统透射模式下的 k 指数最大值偏移了超过 20cm-1。这些发现强调了在反射光谱上使用 KK 算法时需要仔细管理，以避免错误的赋值。另一方面，组合和倍频带（被漫反射增强）被证明能够可靠和敏感地识别大多数所研究的颜料。通过对纯化合物和绘画模型的研究获得的知识随后被用于解释从绘画和手稿中获得的光谱。
