An experimental study of artificial weathering of two outdoor coatings pigmented with natural indigo from Isatis tinctoria was carried out. The two coatings, natural indigo-pigmented boat varnish and outdoor paint, were exposed to cycles of ultraviolet light, water condensation and water spray for 40 days in a QUV test chamber. Synthetic indigo and commercial ultramarine pigment were employed as reference materials. The effects of artificial weathering on the coatings were evaluated with CIELab parameters, as well as visual inspection. Coating and pigment stability during artificial weathering were studied with reflectance spectrometry, hyperspectral imaging technology and Fourier Transform–infrared spectroscopy. According to the results, coatings with indigo proved to be more resistant to visual and spectral changes than unpigmented or commercially pigmented coatings.

中文翻译：

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用板蓝根天然靛蓝着色的木器涂料在加速风化后的颜色稳定性

两种以板蓝根天然靛蓝着色的户外涂料的人工风化实验研究进行了。这两种涂料，天然靛蓝颜料船用清漆和户外涂料，在 QUV 测试室中暴露于紫外线、水冷凝和喷水循环中 40 天。合成靛蓝和商业群青颜料用作参考材料。人工风化对涂层的影响通过 CIELab 参数和目视检查进行评估。使用反射光谱法、高光谱成像技术和傅里叶变换红外光谱研究了人工风化过程中的涂层和颜料稳定性。根据结果​​，靛蓝涂层被证明比未着色或商业着色涂层更能抵抗视觉和光谱变化。