Consolidation of Black-dyed Māori Textile Artefacts: Evaluating the Efficacy of Sodium Alginate

Black-dyed artefacts are found in museums worldwide, many produced using an iron-tannate compound. Deterioration of iron-tannate dyed artefacts is an international preservation issue: in New Zealand the deterioration of paru (iron-tannate) dyed Māori textiles is widespread. This article reports experimental work testing the efficacy of sodium alginate, a consolidant developed for deteriorated paru-dyed muka (fibre from harakeke; Phormium tenax). The colour stability, strength retention, and acidity of paru-dyed muka consolidated with sodium alginate (0.25, 0.5, and 1% w/v in water) was tested pre- and post-artificial light ageing. This study found that sodium alginate had no negative effect on paru-dyed muka and in some cases provided benefit. Interestingly, the colour of paru-dyed muka is substantially more stable in UV-filtered light than previously recognised. Also microfading results were in agreement with visual assessments of colour change at 1 Mlux hour exposure, providing confidence in this relatively new technique to assess colour change.     

Reflections on light monitoring: Evaluating museum lighting options for modern and contemporary art

Spectrometric handheld light meters that can provide adequate data for evaluation of replacement bulbs for contemporary art objects are now commercially available. This approach was taken to assess potential replacements for the incandescent street lamps in Chris Burden's Urban Light at LACMA, Los Angeles, USA. These meters are also useful tools for monitoring and characterizing museum lighting, which are currently done with illuminance (lux) meters. The new spectral light meters will enable conservators to tailor lighting recommendations for individual artworks, when spectral information from these meters is combined with damage function data on artists’ materials. The latter information can be obtained for some materials by a small modification to the microfade testing procedure, as exemplified by microfading colored samples Henri Matisse created during the design phase for La Gerbe.     

Photochemical colour change for traditional watercolour pigments in low oxygen levels

Abstract

An investigation for light exposure on pigments in low-oxygen environments (in the range 0–5% oxygen) was conducted using a purpose-built automated microfadometer for a large sample set including multiple samples of traditional watercolour pigments from nineteenth-century and twentieth-century sources, selected for concerns over their stability in anoxia. The pigments were prepared for usage in watercolour painting: ground and mixed in gum Arabic and applied to historically accurate gelatine glue-sized cotton and linen-based papers. Anoxia benefited many colorants and no colorant fared worse in anoxia than in air, with the exception of Prussian blue and Prussian green (which contains Prussian blue). A Prussian blue sampled from the studio materials of J.M.W. Turner (1775 ? 1851) was microfaded in different environments (normal air (20.9% oxygen) 0, 1, 2, 3.5, or 5% oxygen in nitrogen) and the subsequent dark behaviour was measured. The behaviour of the sample (in normal air, anoxia, and 5% oxygen in nitrogen) proved to be consistent with the 55 separately sourced Prussian blue samples. When exposed to light in 5% oxygen in nitrogen, Prussian blue demonstrated the same light stability as in air (at approximately 21°C and 1 atmosphere). Storage in 5% oxygen is proposed for ‘anoxic’ display of paper-based artworks that might contain Prussian blue, to protect this material while reducing light-induced damage to other components of a watercolour, including organic colorants and the paper support.     

The making of Mark Rothko's Harvard Murals

Mark Rothko's Harvard Murals are a series of paintings on canvas commissioned by Harvard University and created in the early 1960s. The present study investigates Rothko's creative process, materials, and technique with ultraviolet and infrared imaging, analytical chemistry, cross-sectional analysis, and comparisons with the literature. Infrared and Raman spectroscopy imaging of cross sections help with the chemical mapping of the paint stratifications. A comparison of paper studies, studies on canvas, and the final five works installed give a detailed insight into Rothko's editing process. The intimate relationship between works on paper and canvas is traced by uncovering a back and forth between the two media, and the mixing of dry pigment with binder is a common theme for works on both supports. Motif developments, changes, and distinct painting campaigns become apparent with ultraviolet induced visible fluorescence imaging and infrared reflected infrared digital photography. Color measurements and microfading experiments give insight into the stability and light sensitivity of the materials used by Rothko in the Harvard Murals.