Inorganic artists' materials associated with paintings include supports such as: stone (slat slabs, alabaster polychromy); multi-media decorative elements (glass, paste, gems); metallic structural components; and pigments.
The majority of scientific analysis undertaken at the Institute involves the identification of pigments. Artists' pigments include natural and synthetic compounds and can be identified to varying levels of specificity via a number of methods.
Polarised Light Microscopy (PLM)
Polarised light microscopy (PLM) can identify the majority of pigments found in Old Master paintings using very small samples taken from exposed surface layers. The identification of pigments is routinely undertaken by students, interns and staff. In some instances, pigment identification using PLM is definitive, in other cases a generic identification is possible and other techniques may be used if elaboration is required.
Paint cross sections can be used in conjunction with other methods such as PLM, to identify artists' materials and methods. Although some pigments and media can be generically identified in microscopic paint cross sections, they are most useful for determining the artists' techniques, ie. the ways in which materials are used. Paint cross sections can also provide insight into an object's conservation history by revealing how the sample has interacted with its environment or how individual components within the paint layer sample interact with each other.
Scanning Electron Microscopy
Scanning electron microscopy is routinely used to elaborate upon artists' materials. Pigment dispersions (before mounting for PLM), un-mounted samples or paint cross sections embedded in resin and polished can all be examined to determine surface morphologies and the identity and distribution of elements for most pigments.
Where the work of art is sufficiently small (for eg. individual folios from medieval manuscripts or fragments of painted Egyptian papyri) sampling for EDX analysis is unnecessary, as the Institute also has access to an Environmental Scanning Electron Microscope.
The Institute has developed excellent working relationships with a number of renowned experts in various relevant specialist analytical areas and, as a result, we are able to draw upon analytical methods that include, but are not restricted to, the following –
- Gas Chromatography-Mass Spectrometry (GCMS)
- High Pressure Liquid Chromatography (HPLC)
- Fourier-transform Infra-Red Spectroscopy (FTIR)
- Raman Spectroscopy
- Lead isotope analysis
- Trace element identification
- Coccolith identification
Whereas the study of artists' materials results in material identifications of various levels of specificity, the study of artists' methods has a less reductive outcome. Artistic processes are, of necessity, less amenable to unambiguous characterisation than artistic products. Artist's methods are studied using the same scientific techniques that are used in the study of artists' materials, but with a greater reliance on statistical tools. They are also studied by analysing the products of reconstructions.