Assessing the Impact of LED Lighting on the Stability of Selected Yellow Paint Formulations

Light emitting diodes (LEDs) are steadily finding application in an increasing number of museums and heritage institutions, providing energy-efficient solutions for collections display. Although there is a business case to be made for moving toward LED lighting, the safe display of objects must also be ensured. Identifying vulnerable pigments and paints ensures that future preservation strategies will be put in place, avoiding acerbation of damage and reducing the need for conservation. In the first part of our research we investigate color shift and molecular alterations in three yellow paints, namely, lead chromate sulfate, arsenic sulfide, and cadmium sulfide in linseed oil and gum arabic binders. Following an artificial aging regime, color shift was evaluated using colorimetry and molecular alterations were monitored using attenuated total reflectance–Fourier transform infrared spectroscopy coupled with multivariate analysis. Up to 80 Mlux h the lead chromate samples in linseed oil displayed equivalent color shifts approximating 10 ∆E00 on exposure to the three artificial aging regimes. Color shift has been attributed to the formation of lead oxides evidenced by the appearance of a mid-infrared spectral band at 470 cm−1 assigned to PbO2. Above 80 Mlux h the formation of lead oxides was exacerbated by exposure to one particular LED. Arsenic sulfide in linseed oil displayed color shifts intensified by both types of LED. Above 40 Mlux h there was a discernible color shift in all samples, with the two LEDs displaying ∆E00 values two times higher than those displayed by the tungsten halogen samples. The alterations have been attributed to the formation of As2O3, which is known to form in the presence of wavelengths shorter than 428 nm. Cadmium sulfides in both linseed oil and gum arabic paints did not display discernible color shifts or the presence of degradation products.

发光二极管（Light Emitting Diodes，LED）正越来越多地应用于各类博物馆与文化遗产机构，为藏品展示提供节能解决方案。尽管推广LED照明具备商业合理性，但文物的安全展示仍需得到保障。识别易受损的颜料与涂料，有助于制定后续的文物保护策略，避免损伤加剧，同时减少文物修复的需求。在本研究的第一部分，我们针对三种黄色颜料展开了色移（color shift）与分子变化（molecular alterations）分析，这三种颜料分别为硫酸铬酸铅、硫化砷以及硫化镉，载体分别为亚麻籽油与阿拉伯树胶。在经过人工老化处理后，我们通过比色法（colorimetry）评估颜料的色移情况，并借助结合多变量分析的衰减全反射-傅里叶变换红外光谱（attenuated total reflectance–Fourier transform infrared spectroscopy，ATR-FTIR）监测分子变化。当辐照时长不超过80兆勒克斯小时（Mlux·h）时，亚麻籽油载体的硫酸铬酸铅样品在三种人工老化条件下的色移量均约为10个CIEDE2000色差值（∆E00）。色移现象可归因于氧化铅的生成，这一点可通过470 cm⁻¹处出现的归属为二氧化铅（PbO₂）的中红外光谱峰得到证实。当辐照时长超过80兆勒克斯小时时，某一款特定LED的辐照会加剧氧化铅的生成。亚麻籽油载体的硫化砷样品的色移会因两种LED的辐照而加剧。当辐照时长超过40兆勒克斯小时时，所有样品均出现了可观测的色移，且两款LED辐照下的CIEDE2000色差值（∆E00）是钨卤灯样品的两倍。该变化可归因于三氧化二砷（As₂O₃）的生成，已知当辐照波长短于428 nm时会生成该物质。亚麻籽油与阿拉伯树胶载体的硫化镉样品均未出现可观测的色移，也未检测到降解产物。