Prediction of optical radiation-induced damage of white paper in cultural heritage preservation

在所有博物馆、档案馆和图书馆，光暴露是一个紧迫的保存问题，在这些地方，纸质物品经历着越来越多的公开展览和借阅周期。反复要求不可替代的图纸、印刷品、文件和书籍。规划纸质物品的展览视野从根本上取决于光剂量决定。他们必须在当前的展示利益和延长物品使用寿命的长期保存承诺之间取得平衡。对于二维纸质物体，使用寿命主要由它们的对比度和颜色决定，它们是唯一容易阅读的特征，两者都高度依赖于形成所有纸质物体视觉上不可分割的一部分的纸质衬底的空白区域。大多数纸张对象被归类为中等到高度感光，但这主要与媒体有关。除了富含木质素和光亮的类型外，白纸是迄今为止所有纸张收藏中最主要的材料，根据指南，它被认为是稳定的，我们认为这个分类太不区分了。这是我们的起点。我们研究了白纸与老化有关的颜色变化模式，我们已经知道这在很大程度上取决于它的关键成分(含有钙盐、铁离子、明胶、明矾、木质素、光学增白剂的纤维素基)。我们描述了新的和预先老化的白纸类型的成分依赖的、光诱导的老化，通过它们的颜色演变来生成它们未来光响应性的预测模型。所开发的样品用于微衰落测试(MFT)的研究。MFT目前是对文化遗产进行现场剂量反应测试的唯一可用工具。由于MFT在纸张收藏中的使用越来越多，这提出了一个基本但尚未回答的问题：现有的MFT(氙气源)和有前途的新MFT(LED源)是否可以被认为是确定白纸光响应性的合适工具，以及这两种工具中是否有一种在光谱和操作上更适合于这项任务？我们将阐明MFT在纸张对象上使用的意义，优化MFT的一般工作参数，特别是其关于纸张对象的可解释性，并对白纸中的光诱导颜色变化模式产生不同的理解。这将使我们能够为使用纸质收藏的用户制定MFT指南。这一应用科学项目汇集了经验丰富的研究人员、迄今为止唯一的德国MFT用户(柏林，主要申请者/德累斯顿)和遗产保护方面经验丰富的纸质研究人员(斯图加特)。一些合作伙伴已经联合发表了相关主题的文章，都分享了知识转移的经验。他们现在建立在对彼此工作的相互理解和互补的专业知识的基础上，这是他们在三个申请机构--博物馆、实验室和大学--的首次协同努力。

Light exposure is one pressing preservation issue in all museums, archives and libraries where paper objects undergo ever-increasing cycles of public exhibition and loans. Irreplaceable drawings, prints, documents and books are repeatedly requested. Planning exhibition horizons for paper objects depends fundamentally on light dose decisions. They must balance current display interests against the long-term preservation commitment to prolong the objects’ useful lifespan. For two-dimensional paper objects, useful lifespan is determined significantly by their contrast and color as the only readily readable features, both highly dependent on the blank areas of paper substrates that form a visually integral part of all paper objects. Most paper objects are classed moderately to highly light-sensitive, but this primarily concerns media. With the exception of lignin-rich and optically brightened types, white paper, by far the most dominant material in all paper collections, is considered stable by guidelines, a classification we believe is too undifferentiated. This is our starting point. We investigate the aging-related color change patterns of white paper that we already know depend significantly on its key components (cellulosic base with salts of calcium, iron ions, gelatin, alum, lignin, optical brightening agents). We profile component-dependent, light-induced aging of new and pre-aged white paper types by their color evolution to generate a predictive model of their future light responsivity. The developed samples serve our investigation of microfading testing (MFT). MFT is currently the only available tool for in situ dose-response testing on cultural heritage. Because MFT finds increasing use in paper collections, this raises a fundamental and yet unanswered question: can the established MFT (Xenon source) and a promising new MFT (LED source) be considered appropriate tools to determine the light responsivity of white paper, and is one of the two instruments better suited for this task spectrally as well as operationally? We will clarify the significance of MFT for use on paper objects, optimize the working parameters of MFT in general and specifically its interpretability concerning paper objects and create a differentiated understanding of light-induced color change patterns in white paper. This will allow us to formulate MFT guidelines for users who are working with paper-based collections. This applied science project brings together experienced researchers, the to-date only German MFT users (Berlin, main applicant / Dresden) and experienced paper researchers in heritage preservation (Stuttgart). Some of the partners have already published jointly on relevant topics, all share knowledge transfer experience. They now build on their mutual understanding of each other’s work and complementary expertise in their first concerted effort across three applicant institutions – museum, laboratory and university.