Alice V. Turkington

Condition Assessment for building stone conservation: a staging system approach

Abstract Trofimov and Phillips (Geomorphology 5 (1992) 203) suggest that the ultimate goal of any science is to predict the behaviour of entire systems. With regard to the decay of building stone, making accurate predictions of stone behaviour remains an elusive goal but given our improved understanding of decay dynamics it should be possible to provide a forecast of likely system behaviour. However, forecasting system behaviour requires classification of the system state with the classification, whether formal or informal, founded on knowledge of the factors that control response. In the context of building stone decay these controlling factors include, structural properties, mineralogical properties, inheritance effects, contaminant loading and natural change. In trying to formalise building stone condition assessment and incorporate a forecast component, an analogy can be made between the requirements for classification and treatment determination of cancer patients and the approach to condition assessment and conservation of stone structures. In medicine, one of the most widely used and refined patient assessment schemes is the TNM Staging System. The rationale underpinning the TNM Staging System has many similarities with approaches to building stone assessment in that it seeks to impose a more formal structure on condition assessment that provides a commonality of approach, language and meaning and a procedure for forecasting the extent of remedial intervention required and outcome in terms of ‘life expectancy’.

Surface change and decay of sandstone samples exposed to a polluted urban atmosphere over a six-year period: Belfast, Northern Ireland

Abstract Test blocks of a siliceous sandstone (Dunhouse sandstone) and a calcareous sandstone (Baumberger sandstone) were mounted in vertical aluminium racks, both sheltered and exposed to rainwash, in a range of locations within the Belfast urban area, Northern Ireland, UK. Blocks were retrieved after 3 months, 2 years, 4 years and 6 years of exposure. Visual and chemical analyses of the sandstone samples revealed a variable response to polluted atmospheric conditions, dependent on stone type and exposure conditions. An exponential increase in salt content was recorded in several sheltered samples; exposed samples displayed an inconsistent change in salt content over time. Visual analysis by scanning electron microscopy demonstrated variable amounts of gypsum crust development, biological growth and depositional material. Results indicate that stone surface alteration in a polluted atmosphere may be significant during initial exposure of fresh or cleaned stone.

Setting stone decay in a cultural context: conservation at the African Cemetery No. 2, Lexington, Kentucky, USA

Abstract Management of stone artifacts requires understanding the driving forces for change, whether natural or anthropogenic, in order to implement effective conservation strategies. Physical, chemical and biological processes of stone decay must be understood in order to remediate the damage they cause. It is not merely the stone itself which is to be conserved, however, but also the cultural, social, religious or artistic ideas that it represents; these values are changeable and must be defined in the context of contemporary heritage processes. Cemetery stone in Kentucky, USA, provides an example of the importance of a holistic approach to stone conservation, which integrates scientific knowledge of decay processes with conservation theory and the needs of stakeholders.

Weathering Geomorphology: Theoretical and Methodological Themes

The history of geomorphic thought may be summarized as a series of dominant theoretical or methodological trends consisting of natural law and classification, W. M. Daviss geographical cycle and denudation chronology, process geomorphology, systems analysis, and the more contemporary nonlinear dynamical systems approaches. This history may be an apt description of the development of certain geomorphic subfields over the last 100 years, but it does not properly describe the history of rock weathering research. Despite being an integral component of much geomorphic work, the focus of weathering geomorphology has been on qualitative research, with less emphasis on geomorphic theory. This anomalous development is in part a reflection of the specific research questions addressed and the availability or adoption of analytical techniques. Additionally, the differing path reflects the applied nature of the research conducted and disciplinary differences between weathering researchers and other geomorphologists. The authors call for a closer examination of the historical developments and trends within all subfields of geomorphology in order to provide a better understanding of the discipline itself. In terms of weathering geomorphology, there is also a need for greater promotion of the importance of weathering processes to geomorphologists and recognition of disciplinary commonalities.