Postgraduate Dissertation
Working Title: ‘A Recipe for Deterioration: How Precipitation Route and Extraction Method Govern Ageing Characteristics and Carboxylate Formation in Reconstructed Hydrated-Alumina Madder Lakes’
Extended Abstract:
'The instability of madder lake pigment upon ageing within oil paint films has long been recognised, however, the effect of variations in its manufacture on such instability has not been investigated. In particular, the possibility that this pigment’s hydrated alumina substrate might itself contribute to the formation of metal carboxylates upon ageing has not been addressed. The present study examines how the production route of a reconstructed historical madder lake governs the composition of the finished pigment and its ageing characteristics within an oil paint film. Hydrated-alumina madder lakes were reconstructed using three recipes, selected so that the method in which the dye was extracted and the route by which the reagents were precipitated could each be varied while the other was held constant. Each reconstructed pigment, as well as two commercial reference madder lakes, was ground into linseed oil to form a paint film and, separately, into a Paraloid® B72 medium. These variants were then characterised prior to, and following, accelerated light ageing through pH measurement, stereomicroscopy, spectrophotometry, ATR-FTIR, SEM with EDS, and a carboxylate solubility test.
The extent of carboxylate formation upon the ageing of the reconstructed paint films was found to be governed by precipitation route, with carboxylate growth being greatest for the acid-first recipe pigments and smallest for the two alkali-first variants. The metal carboxylate species observed formed within an aluminium-dominated paint matrix and its spectral bands were broad in profile rather than sharp, indicative of an amorphous or ionomer-like metal soap. The solubility test conducted on these instances of soap formation failed to recover any water-soluble carboxylates, consistent with the presence of an insoluble aluminium carboxylate, but the cation could not be definitively assigned. Total colour change followed the same route-dependent ranking, but this behaviour was mediated by the oil binder and independent of the extent of soap formed. Extraction method, in turn, governed the proportion of substrate to dye present in the reconstructed pigments, but such differences were not highlighted upon ageing within the present data. In this way, the study establishes precipitation route as a determinant of metal soap formation in madder lake oil paint films, recasting the pigment’s deterioration as a consequence of its production method, rather than of the dye alone. In doing so, it draws conservators’ attention to a mechanism by which a common pigment degrades from within and which may serve to reframe how such deterioration is recognised, anticipated, and most effectively managed.'
Research Gallery:
Undergraduate Dissertation
Painting the ‘Absent’ In Gitxsan Territory: Pegi Nicol, Skeena Landscapes, and the Indigenised Production of Canadian National Identity in the 1920s chronicles the way in which artists were encouraged to draw upon Indigenous imagery, relegated to a distant romantic past and supposedly on the cusp of disappearing altogether, to produce a 'unique' visual culture for the young Dominion of Canada. This is achieved via a multidisciplinary approach which responds to both art historical and anthropological frameworks.
Final Grade: 18.5/20