Tutor(s): David Saunders
Places available: 30
Location: British Library
The day offers a brief summary of the principles behind, and advantages of, some of the most commonly-encountered non-invasive methods and their application to the examination and analysis of different types of museum objects, including works on paper, paintings, sculpture and archaeological collections. It is not intended to provide training in their use, but rather to offer an understanding of the type of information produced by each method so that appropriate techniques can be chosen to address questions that arise during the study, conservation or analysis of museum objects. Descriptions of the principles of each method are illustrated by case studies on a broad range of different types of museum object.
The programme is divided into five sections:
An introduction to non-invasive methods
The characteristics of non-destructive, non-invasive and non-contact techniques are defined. The differences between examination and analysis are also defined.
Reasons for choosing or preferring non-invasive methods are presented as is the need to balance the information gained with the degree of intrusion and the practical considerations required when selecting appropriate techniques
Non-invasive techniques must interact with objects without (greatly) affecting their molecular and physical integrity. Most methods rely on the interaction of electromagnetic radiation with materials. Radiation, radiation sources and detectors are introduced as are the concepts of absorbance, reflectance, transmittance, refraction, diffraction, luminescence, interference and scatter. The interaction of matter with particles is discussed, including the analogous phenomena of absorbance, diffraction and fluorescence.
Methods for 2D examination
Two-dimensional methods look principally at the surface of objects without considering their topography. They include many methods that were traditionally photographic processes, including visible light, ultraviolet, infrared and false colour imaging. Luminescence imaging techniques, including ultraviolet fluorescence imaging are also described. Although used to examine sub-surface phenomena, infrared reflectography and transmitted light imaging are covered by this section.
Methods for 3D examination
Two types of 3D examination are considered. First, methods that record the surface topography of objects, including raking light imaging, reflectance transformation imaging (RTI), photogrammetry and laser imaging. A second group of methods maps the 3D structure of the entire object, either by providing a ‘collapsed’ 2D image, as in X-radiography, β-radiography or neutron radiography, or by presenting a 3D rendering of the entire structure through computed tomography (CT). The technique of optical coherence tomography (OCT) is also considered here.
The final section explores some common methods for non-invasive elemental and molecular analysis. Elemental methods include X-ray fluorescence (XRF), both as a technique for spot analysis and as a means of mapping elemental distribution across an object. Particle-induced fluorescence methods are also considered briefly. The non-invasive molecular methods described include Fourier transform infrared (FTIR) and Raman spectroscopy. The potential for using these methods to map materials across objects is considered and the rapidly-evolving technique of hyperspectral imaging (imaging spectroscopy) concludes the day.