A holistic multimodal approach to the non-invasive analysis of watercolour paintings

TL;DR

This paper presents a comprehensive non-invasive multimodal imaging and spectroscopic approach to analyze 19th-century Chinese watercolour paintings, combining multiple techniques to identify materials and techniques for conservation and historical insights.

Contribution

It introduces an integrated multimodal methodology combining VIS-NIR, multispectral imaging, micro-Raman, XRF, and OCT for detailed analysis of watercolour paintings.

Findings

Techniques complement each other in pigment and material identification.

The approach provides extensive information for art conservation.

Assessment of paintings' vulnerability to light exposure was achieved.

Abstract

A holistic approach using non-invasive multimodal imaging and spectroscopic techniques to study the materials (pigments, drawing materials and paper) and painting techniques of watercolour paintings is presented. The non-invasive imaging and spectroscopic techniques include VIS-NIR reflectance spectroscopy and multispectral imaging, micro-Raman spectroscopy, X-ray fluorescence spectroscopy (XRF) and optical coherence tomography (OCT). The three spectroscopic techniques complement each other in pigment identification. Multispectral imaging (near infrared bands), OCT and micro-Raman complement each other in the visualisation and identification of the drawing material. OCT probes the microstructure and light scattering properties of the substrate while XRF detects the elemental composition that indicates the sizing methods and the filler content. The multiple techniques were applied in a study of forty six 19th century Chinese export watercolours from the Victoria & Albert Museum (V&A) and the Royal Horticultural Society (RHS) to examine to what extent the non-invasive analysis techniques employed complement each other and how much useful information about the paintings can be extracted to address art conservation and history questions. A micro-destructive technique of microfade spectrometry was used to assess the vulnerability of the paintings to light exposure.