ABSTRACT Round and ring-shaped abrasions and whitish islands were observed with a digital microscope in a degraded area of blue paint in Jan de Bray’s (1626/7–1697) Judith and Holofernes, 1659, a Dutch panel painting from the collection of the Rijksmuseum in Amsterdam. Although whitish islands have been previously reported as degradation deposits in ultramarine paint layers, it was unclear in this painting if the islands were remains of abraded paint, degradation deposits, or both. Non-invasive and micro-sampling techniques were used to study the materials and damage phenomena. Two blue pigments were identified in the blue blanket: indigo and ultramarine. The whitish islands were characterized as remnants of an abraded and degraded ultramarine paint layer used for the midtones and highlights on top of an indigo-containing blue-gray underlayer. The authors propose a possible mechanism for discoloration and damage to the ultramarine paint layer. Deposits of palmierite, a lead-potassium-sulfate compound, were also detected in the blue paint layers of the blanket but are not considered a significant component of the whitish islands. The likely presence of alum in the indigo may explain a UV-induced visible fluorescence observed in the indigo-containing paint layers. Ultimately, the results of the study were used to inform the retouching stage of treatment.

中文翻译：

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Jan de Bray的Judith和Holofernes的蓝调：两种蓝色颜料的技术研究及其对治疗的影响

摘要在1659年1月1日于贾德思和霍洛弗涅斯（Judi de and Holofernes）于1659年从荷兰国立博物馆收藏的荷兰壁画中，用数字显微镜在蓝色油漆的退化区域内观察了圆形和环形擦伤和发白的岛。在阿姆斯特丹。尽管以前有报道说白色岛屿是群青油漆层中的降解沉积物，但在这幅画中尚不清楚这些岛中是否残留有磨损的油漆，降解沉积物或两者兼有。非侵入性和微采样技术被用来研究材料和破坏现象。在蓝色毯子中发现了两种蓝色颜料：靛蓝和群青。发白的岛的特征是用于中间调的磨损和退化的群青漆层的残余物，并在包含靛蓝的蓝灰色底层上突出显示高光。作者提出了一种可能的机制，使群青漆层变色和损坏。在毯子的蓝色涂料层中也检测到了铅铝硫酸铅化合物棕铁矿的沉积物，但这些沉积物不被认为是发白岛的重要组成部分。靛蓝中可能存在明矾可能解释了在含有靛蓝的涂料层中观察到的紫外线诱导的可见荧光。最终，研究结果被用于告知治疗的修饰阶段。靛蓝中可能存在明矾可能解释了在含有靛蓝的涂料层中观察到的紫外线诱导的可见荧光。最终，研究结果被用于告知治疗的修饰阶段。靛蓝中可能存在明矾可能解释了在含有靛蓝的涂料层中观察到的紫外线诱导的可见荧光。最终，研究结果被用于告知治疗的修饰阶段。