Ian MacLeod

Conservation treatment and associated scientific analysis of a significant pretiosa (Latin, precious) mitre from the Benedictine Monastery at New Norcia, Western Australia is presented. Analysis of the pH and surface chloride readings showed that increased acidity contributed to the deterioration of the silk fibres, which could be directly related to the levels of retained sweat indicated by the measured chloride ion activity. Migration of acidity from the external silk fabric into the oiled cardboard internal stiffeners necessitated the insertion of replica pieces into the subsequently disassembled mitre. Prior to this work, the corroded gilded silver alloy decorative elements on the disassembled mitre were conserved in situ through reductive consolidation in a 0.1 wt. % sodium dithionite solution at neutral pH. Considerable couching was conducted to stabilise the metalwork and the damaged silk panels on both faces of the mitre, owing to extensive wear from repeated and extended use. Extensive biological degradation of the original silk lining had rendered the original materials with insufficient structural strength to undergo conservation treatment, ultimately requiring replacement with a matching modern silk. All original materials were kept as part of the research collection held by the New Norcia community to allow for future possible DNA analyses.

The application of statistical sampling of a large collection of ecclesiastical textiles at the monastic Benedictine community at New Norcia, Western Australia produced a reliable indicator for the overall significance of the collection to the Australian people. By grouping the main types of garments into distinct functional categories it was possible to apply a ten per cent sample size to groups of objects that numbered in excess of 100 items. Middle sized groups were sampled at approximately 20% and small samples were all assessed. During the examination of the garments the conservation needs were also reviewed. The same condition range of conservation needs was used as in the significance matrix, with 5 being the most significant or the most in need of conservation and restoration work to stabilise the collection items. The distribution of significance was found to follow a logarithmic relationship between the numbers in each category and the significance unit values ranging from one to five. The conservation needs analysis showed that nearly 80% of the collection could be stabilised with simple preventive conservation methods practised by trained volunteers. The combined values of the significance and conservation needs formed the two arms of a decision matrix that determined the priority and needs assessment of the collection items. The combination of the conservation and significance rankings facilitates a rational decision process for prioritisation of treatment.

... Titre du document / Document title. In situ corrosion studies on iron shipwrecks and cannon. ... Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). (1) Department of Materials Conservation,Western Australian Museum, Fremantle, Western Australia 6160, AUSTRALIE ...

Abstract-Identification of corrosion products on non-ferrous metal artifacts recovered from historic shipwrecks off the coast of Western Australia has provided conservators with useful information regarding the nature of the degradation processes on copper, brass, bronze, silver, lead ...

Microclimate data from typical sandstone and limestone rock art sites in the west Kimberley region of Western Australia were recorded in both the wet and the dry seasons. The research described in this paper shows that the climatic behaviour in rock shelters is more amenable to direct interpretation when the relative humidity at any given temperature is converted to absolute humidity or water vapour pressure. It has been shown that many of the sites act as 'closed systems' with little input or output of moisture until water bearing fronts or drying winds change the local microenvironment. The rate of cooling of points within the shelters is largely determined by exposure to the sky, which facilitates cooling by emission of long wave radiation and by the heat capacity of the moisture in the air. It was found that the heating and cooling rates for limestone sites in the Napier Ranges are more sensitive to changes in moisture than the sandstone sites in the Mitchell Plateau. Th...

The former Australian Naval vessels, HMAS Swan and HMAS Perth were scuttled as artificial reefs off the Western Australian coast in 1997 and 2001, respectively. In addition, the former HMAS Hobart was sunk in Gulf St Vincent, South Australia in 2002. During the preparation of the ships prior to sinking, significant quantities of metals, such as copper, copper alloys, aluminium, lead and steel, petroleum hydrocarbons and other potential pollutants were removed. Since it is possible that corrosion products and residual hydrocarbons may impact on the local marine environment, corrosion and sediment monitoring programmes were implemented on each of the three vessels. The concentrations of heavy metals, total petroleum hydrocarbons and butyl tins in the surrounding sediments were periodically monitored. The results demonstrate synergistic interactions between modern shipwreck materials, sediments, biota and the marine environment and the long-term stability of the vessels.

... Author: MacLeod, Ian Title Article/Chapter: "Rock art conservation and management: the past, present and future options" Title of Source: Reviews in conservation Issue Number: 1 Date of Publication: 2000 Page Numbers: 32-45 ISSN: 1605-8410 Language Text: English ...

ABSTRACT The primary function of this review is to provide the reader with an overview of the issues that impinge on the conservation management of rock art sites around the world. Because of the author~s familiarity with Australian rock art sites~ particularly those in the Kimberley region of Western Australia~ the review is somewhat slanted towards Australian issues. The first section covers factors associated with the basic points of documentation, which includes the sites themselves as well as the images painted or engraved on the rock surfaces. Techniques range from the rudimentary methods of sketching and tracing to the use of photogrammetric, photographic, videographic and colourimetric methods of documenting both the nature of the surfaces and the way in which the images have been presented. The involvement of indigenous persons in all the areas of documentation and any subsequent intervention at the site or on the images is considered to be most important. Detailed discussion of the role of controlling visitor access indicates that this is a primary factor influencing the deterioration of rock art sites~ whether they are in subterranean environments or in open shelters. Management of the natural factors of the impact of flora and fauna and human visitation at the sites are discussed and some simple and practical options for cost-effective management are provided. The importance of recording base-line information about the microclimate, in terms of the temperature and relative humidity, are frequently stressed. The roles of bacteria, lichens and moulds are reported, with some guidance as to how the relative importance of these forces of decay varies with the nature of the site. The next section contains a detailed discussion regarding the nature of the pigments that have been used in the execution of the paintings and how these minerals and other products have undergone changes. Not all natural ageing processes lead to the irreversible deterioration of the images. Examples of beneficial weathering are given as illustrations of the need to identify carefully the nature of the materials on the surface, in the substrate and in the immediate microenvironment before reaching any decisions as to the nature of the site. The impact of graffiti and the removal of the same is reviewed in the context of overall visitor and site management. The final section covers the primary role of water as the principal agent of decay of the painted surfaces. This can be in the form of direct dissolution of the rock substrate, erosion, salt efflorescence and the promotion of bacterial and algal activity. The concluding chapter offers some comments on the future directions in the management of rock art sites and the need for continuing research.