Mark Richter of the TAHG is currently leading the scientific investigation of the five related sixteenth-century Spanish portraits in the Stirling Maxwell Collection for this project. The results will be compared with those for the Lady in a Fur Wrap, which underwent technical examination using the world-class, and in many cases, state-of-the-art facilities and expertise at the Museo Nacional del Prado, Madrid in 2014, as well as with those for other paintings in the Prado and elsewhere. Though there is no guarantee of definitive results, detailed comparative assessment and discussion will most likely provide us with valuable and new information on artists’ materials and techniques of these paintings as well as further insights on studio practice of sixteenth-century Spanish portraiture.
The scientific examination is a collaboration involving several partners and international specialists. It includes examination of the paintings’ surface with stereomicroscopy and other imaging techniques at Glasgow Museums (raking light photography, ultraviolet light photography and infrared photography), as well as the study and analysis of microscopic paint samples (paint cross sections) in the research laboratories of the TAHG and the Imaging Spectroscopy and Analysis Centre (ISAAC) at the University of Glasgow, using optical microscopy, fluorescent staining and scanning electron microscopy coupled with energy-dispersive X-ray microanalysis (SEM-EDX).
X-radiography of the paintings has been carried out at the University’s School of Veterinary Medicine. With no dedicated facilities for X-raying paintings throughout Scotland, this newly established partnership provides a welcome opportunity for the team to analyse aspects of artworks not visible to the naked eye. The X-ray process should provide information about the artist’s materials and techniques, as well as revealing more about an artist’s particular style (e.g. application of aperejo and imprimación) and possible changes that may have occurred at different stages in the development of the paintings being studied.
Using the X-radiography results it is also possible for the Prado to study the canvas support of each painting in great detail, especially the type of weave and the thread densities, using averaged power spectral density (PSD). This approach yields accurate results in thread counting and is very useful for comparing the canvas supports being studied in this project and elsewhere (e.g. Museo Nacional del Prado, Madrid). Historic Environment Scotland are also contributing to the research by providing specialist staff and equipment: Infrared Reflectography (IRR), which may help detect preliminary sketches or underdrawings by artists; and X-ray fluorescence (XRF), which can help to analyse the chemical elements present in the materials used to create the paintings.
Additional advanced analytical techniques are being performed by other external partners. The Doerner Institut, Munich, is undertaking Gas Chromatography Mass Spectrometry (GC-MS) and Amino Acid Analysis (AAA), two techniques that are ideal for providing detailed chemical information on the organic materials found in paint samples, especially binding media. Fourier Transform Infrared imaging (FTIR-imaging) will be carried out at Bern University of Applied Sciences in their Art Technological Laboratory to allow for a more detailed analysis providing layer and site-specific information as well a much more secure interpretation and understanding of the analytical results obtained with GC-MS, AAA and fluorescent staining.
The Stirling Maxwell Spanish Paintings Project is a collaboration between the University of Glasgow, Glasgow Museums and the National Trust for Scotland, with the support of the Museo Nacional del Prado, Madrid.