Conservation varnishes at the National Gallery: studying their optical and material properties

国家美术馆的保护清漆：研究其光学和材料特性

• 批准号: 1947812
• 金额: --
• 依托单位: Nottingham Trent University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1947812
• 关键词: Conservation; varnishes; National; Gallery; studying

Historically and today, conservation varnishes based on natural or synthetic resins are applied to most Old Master paintings after cleaning and restoration. Such varnishes alter a painting's appearance, saturating the surface and reducing variation in gloss, and provide a protective coating. However, the optical, chemical and physical properties of such varnishes can alter with time, leading to changes in the behaviour of the varnish and the appearance of the painting. Currently, our understanding of such changes is largely based on experimental studies (often involving accelerated ageing experiments) or on the expected properties of the bulk resin or polymer, which do not always accurately reflect the long term behaviour of thin films of conservation varnishes. Furthermore, it has become apparent that in practical usage, conservators often have to make adjustments to varnish formulations (e.g. choice of resin, solvents or additives or the combined use of resins as layered systems or blends) in order to obtain a satisfactory appearance of the varnished painting. This project will investigate the actual properties of conservation varnishes, in order to be able to predict more accurately how conservation varnishes behave in practical usage and how their properties might be improved or modified for particular applications, based on the use of cutting-edge non-invasive optical imaging and spectroscopic techniques including optical coherence tomography (OCT) to allow a (non-subjective) assessment of the appearance, condition and properties of both existing varnishes and experimental systems. OCT produces 3D images ('virtual cross-sections) of surface and subsurface microstructure of transparent and semi-transparent materials and has shown promise for research on varnishes on paintings. OCT and other non-invasive portable equipment, as well as chemical analysis with more traditional laboratory equipment, will be used to investigate the effect of not only of the choice of resin but also the practical issues of formulation and application method on the properties (including surface roughness, scattering, layer thickness, transparency, yellowing, elasticity, refractive index and glass transition temperature) of the resulting conservation varnish. The research will draw on both the unique resource of the actual, naturally aged conservator-applied varnishes on the Gallery's paintings and experimental systems in which formulations and application method can be explored by studying film formation processes and the optical and physical properties of the resulting film. The research outcomes have the potential to feed directly into conservation practice at the National Gallery and around the world.

历史上和今天，大多数大师的古画经过清洗和修复后，都会使用基于天然或合成树脂的保护清漆。这种清漆改变了绘画的外观，使表面饱和，减少了光泽的变化，并提供了一层保护层。然而，这种清漆的光学、化学和物理特性会随着时间的推移而变化，从而导致清漆的行为和绘画外观的变化。目前，我们对这种变化的理解主要是基于实验研究(通常涉及加速老化实验)，或者基于主体树脂或聚合物的预期性能，这并不总是准确地反映保护性清漆薄膜的长期行为。此外，很明显，在实际应用中，为了获得令人满意的清漆外观，养护人员经常必须调整清漆配方(例如，选择树脂、溶剂或添加剂，或将树脂作为分层体系或混合物组合使用)。该项目将调查保护清漆的实际性能，以便能够更准确地预测保护清漆在实际应用中的行为，以及如何针对特定应用改进或修改它们的性能，基于尖端的非侵入性光学成像和光谱技术，包括光学相干断层扫描(OCT)，以允许对现有清漆和实验系统的外观、状况和性能进行(非主观)评估。OCT生成透明和半透明材料表面和亚表面微结构的3D图像(虚拟横截面)，并显示出在绘画清漆研究方面的前景。使用OCT和其他非侵入性便携式设备，以及使用更传统的实验室设备进行化学分析，将不仅调查树脂选择的影响，还将调查配方和涂装方法的实际问题对所生成的保护清漆的性能(包括表面粗糙度、散射、层厚、透明度、泛黄、弹性、折射率和玻璃化转变温度)的影响。这项研究将利用画廊油画上的实际自然老化清漆的独特资源和实验系统，在实验系统中，可以通过研究成膜过程和所得薄膜的光学和物理性质来探索配方和应用方法。研究成果有可能直接应用于国家美术馆和世界各地的保护实践。