Vincent Otieno-Alego

The use of radiation for the study of material of cultural heritage significance

Abstract For the indigenous people of Northern Australia the expression of their experience of life, their “dreaming”, is in the form of painting, usually on the bark stripped from trees growing in their tribal lands. These are often works of great beauty and the major collecting institutions in Australia and elsewhere have significant holdings of Aboriginal bark paintings. A wide range of analytical techniques (optical microscopy, FTIR microscopy, Raman microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and synchrotron radiation X-ray diffraction) has been used in a project to determine how best to conserve Aboriginal bark paintings.

In Situ and Laboratory Studies of the Ageing of Protective Wax Coatings on Metal Surfaces of Museum Objects and Outdoor Statues

A variety of waxes have been used by conservators for the preservation of objects of cultural heritage significance in the custody of museums. These waxes are required to behave reversibly when applied to surfaces: they must be readily applied to surfaces, be easily removed, and be robust. Techniques used for the in situ and laboratory study of the degradation of waxy coatings were electrochemical impedance spectroscopy and Raman imaging microscopy. Ex situ techniques included electron microscopy (SEM & TEM) and atomic force microscopy. This paper reviews studies, in situ and ex situ, of changes in the integrity of a number of different wax coatings used by museum conservators. These include such commercial preparations as Besq 195, Cor-Trol 400, Dinitrol 4010 and their use in environments ranging from inside museums to external sites both inland and by the seaside.

Micro-Raman Identification of Bloom Formed on a Historical Print Artifact

Abstract An 1876 engraved birds-eye view of Adelaide, the Calvert Panorama, was submitted to conservators after large quantities of loose white powder were noticed on the surface of the print and the overlying glazing. Previous conservation treatment had occurred in 1972, but no detail was given of the treatment processes. To establish what past treatments may have been applied and to prevent possible exposure to toxic materials, scientific analysis of these solids was performed. As described in this article, micro-Raman spectroscopy was employed to characterize the solid particles that composed the bloom. The unparalleled high spatial resolution (approximately 1 μm) of the technique ensured individual compound identification from a mixture of 4–60 μm-sized particles. No sample preparation was required. The analysis revealed that the bloom was predominantly paratoluenesulfonamide (the residue of chloramine-T, a chemical popular for bleaching paper in the 1960s and 1970s) and calcite, arising from the original deacidifier (calcium hydroxide). Traces of three other species—carbon black, yellow quartz, and cellulose—were also observed. None of the solids identified was a toxic pesticide residue as had been feared.

X-ray reflectivity and grazing incidence diffraction studies of the adhesion of protective wax coatings on metal surfaces

Abstract More than 50 years after the introduction of water displacing petroleum additives for corrosion protection, scientists are still trying to understand how and why they work. This paper continues research on corrosion preventatives used on objects in museum custody using synchrotron radiation techniques to assess the thickness and organization of the protective layers of corrosion preventative. The organization of sodium dodecylsulphate on aluminium, zinc and platinum surfaces has been studied. As well, preliminary in situ experiments using synchrotron radiation have been undertaken on electrode processes in an electrochemical cell using platinum electrodes and a sodium sulphate solution at different applied potentials.

The truth is in there: Analysis of grave relics to help solve a mystery linked to the loss of the HMAS Sydney II

Abstract In February 1942, three months after the HMAS Sydney II sank off the coast of Western Australia, taking with it all 645 crew members, the unidentified body of a man washed ashore in a Carley float on Christmas Island. The body was buried and two eyewitness accounts of the situation recorded. A 2006 recovery mission to find the grave site and give the unknown sailor a proper burial was successful. Relics found in the original grave included four somewhat degraded and corroded press-studs–the only remaining components of the sailor’s clothing. These relics were accessioned into the Australian War Memorial’s collection. Analysis of some of the press-studs was conducted in an attempt to help determine who this sailor may have been, or whether he was likely to have been from the HMAS Sydney II. Elemental and molecular analyses using a range of instrumental techniques including X-ray fluorescence (XRF), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray tomography, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) have been conducted in conjunction with the Australian Federal Police and Australian National University. Strong evidence for an inscription on one of the press-studs and a blue colourant from fragments of fabric preserved within the press-studs have been revealed.

Characterisation of the Moisture Absorption and Thermal Ageing Behaviour of Polymeric Composite Systems Using Raman Spectroscopy

Advanced polymeric materials and their respective composites are fast becoming one of the world’s most frequently used engineering materials. They find application in the manufacture of e.g. boat hulls, high performance motor vehicles, aircraft components and sports goods. Their high specific strength and specific stiffness give them the edge in applications where weight savings are critical, but their long-term durability is often questioned. These materials are susceptible to environmental conditions such as temperature and humidity. There is also a lack of relevant data, due to the long time-scales required for testing. In this study, the Raman technique has been used to monitor the degradation of two composite systems, namely: a rubber toughened vinylester material used in the marine industry and a high temperature bismaleimide/carbon fibre aerospace composite. Preliminary Raman studies show that the toughening rubber particles dispersed in the cured vinylester resin are leached out during hygrothermal ageing. The weight gain during ageing suggests that this leaching process occurs concurrently with the absorption of water molecules. An increase in the degree of cross-linking is observed when bismaleimide/carbon fibre composite is aged at high temperature. This cross-linking tendency decreases with increasing depth within the carbon fibre bundle.