Goltz Douglas, McClelland Jennifer, Schellenberg Angela, Attas Michael, Cloutis Edward, Collins Cathy
C-SCAPE: Centre for Scientific and Curatorial Analysis of Painting Elements, Department of Chemistry, University of Winnipeg, 515 Portage Ave., Winnipeg, Manitoba, Canada, R3B 2E9.
Appl Spectrosc. 2003 Nov;57(11):1393-8. doi: 10.1366/000370203322554563.
Lead white is an historically important paint used by artists since antiquity. The darkening of lead white has been well documented in works of art such as paintings. In this paper, mid-infrared (MIR) and visible spectroscopy were used to examine spectral changes accompanying the darkening of lead white paint as a result of exposure to H2S(g). Laboratory-prepared paint and a commercial lead white paint were used to observe the darkening reaction over time. Structural changes to the pigment, 2PbCO3.Pb(OH)2, in lead white were readily detected using MIR by applying a thin film on a KBr pellet. Spectral changes at 3541 (O-H stretch), 1400 (C-O), and 680 cm-1 (C-O) were the most significant over time as the paint darkened. Visible spectra were also collected to provide a semi-quantitative measure of color change with structural changes observed by MIR. Experiments in the visible region were also conducted to compare the spectral response as % reflected and % transmitted light as lead white darkened. The effect of different binding agents (egg tempera, linseed oil, water, and gum Arabic) on the rate of darkening of lead white was also examined. Other sulfur-containing pigments such as orpiment and realgar were also tested for their ability to darken lead white. By applying paint as a thin film inside a sealed cuvette, darkening of lead white was observed in the visible spectra (800 nm) when either powdered orpiment or realgar was in placed in the cuvette for 24 h.
铅白是一种历史上很重要的颜料，自古以来就被艺术家们使用。铅白的变黑现象在诸如绘画等艺术作品中已有充分记载。在本文中，利用中红外（MIR）光谱和可见光谱来研究由于暴露于H2S（气体）导致铅白颜料变黑时伴随的光谱变化。使用实验室制备的颜料和一种商用铅白颜料来观察随时间的变黑反应。通过在溴化钾压片上涂覆薄膜，利用中红外光谱很容易检测到铅白中颜料2PbCO3·Pb(OH)2的结构变化。随着颜料变黑，3541（O - H伸缩振动）、1400（C - O）和680 cm-1（C - O）处的光谱变化最为显著。还收集了可见光谱，以提供随着中红外光谱观察到的结构变化而产生的颜色变化的半定量测量。还在可见光区域进行了实验，以比较随着铅白变黑时作为反射光百分比和透射光百分比的光谱响应。还研究了不同粘合剂（蛋彩画颜料、亚麻籽油、水和阿拉伯树胶）对铅白变黑速率的影响。还测试了其他含硫颜料，如雌黄和雄黄使铅白变黑的能力。通过在密封比色皿内将颜料涂成薄膜，当将粉末状雌黄或雄黄放入比色皿中24小时时，在可见光谱（800 nm）中观察到铅白变黑。
