Gilbert B, Denoël S, Weber G, Allart D
University of Liège, Analytical Chemistry and Electrochemistry, Bldg. B6C, Sart Tilman, Liège B-4000, Belgium.
Analyst. 2003 Oct;128(10):1213-7. doi: 10.1039/b306138h. Epub 2003 Sep 29.
In the majority of the literature describing green coloured materials used on ancient painting layers (15th or 16th century), two copper greens are mainly cited: malachite [CuCOr3 x Cu(OH)2] and verdigris [Cu(CH3COO)2 x [Cu(OH)2]3 x 2H2O]. It is shown, by micro-Raman spectroscopy, that the artists were actually employing more than these two copper greens, in particular various copper sulfates, among which the most common pigment found is posnjakite [CuSO4 x 3Cu(OH)2 x H2O]. In contrast to the PIXE (particle induced X-ray emission) technique, Raman spectroscopy is a technique of choice, able to distinguish not only a copper sulfate from a carbonate or acetate but also the different sulfates themselves; in this respect, we found that the high wavenumber region (2800-4000 cm(-1)), characteristic of H2O vibrations, is of particular interest. It is also shown that numerous green areas were created with mixtures of a copper sulfate mixed with other pigments, for instance to enhance the colour depth. Finally, in some cases, no green pigment is actually employed but the colour is obtained by intimately mixing yellow and blue pigments. All these results led to a new look at the pigments which were in use on the palettes of the ancient artists.
在大多数描述用于古代绘画层（15世纪或16世纪）的绿色材料的文献中，主要提到了两种铜绿：孔雀石[CuCO₃·Cu(OH)₂]和铜绿[Cu(CH₃COO)₂·[Cu(OH)₂]₃·2H₂O]。显微拉曼光谱显示，艺术家们实际使用的铜绿不止这两种，特别是各种硫酸铜，其中发现最常见的颜料是水硫酸铜[CuSO₄·3Cu(OH)₂·H₂O]。与粒子诱导X射线发射（PIXE）技术不同，拉曼光谱是一种首选技术，不仅能够区分硫酸铜与碳酸盐或醋酸盐，还能区分不同的硫酸盐本身；在这方面，我们发现水振动特征的高波数区域（2800 - 4000 cm⁻¹）特别有趣。还表明，许多绿色区域是由硫酸铜与其他颜料混合而成的，例如为了增强颜色深度。最后，在某些情况下，实际上并未使用绿色颜料，而是通过将黄色和蓝色颜料紧密混合获得绿色。所有这些结果使人们对古代艺术家调色板上使用的颜料有了新的认识。
