Ineducable us: the applications and contexts of microscopy used for the characterisation of historic building materials

John Hughes

doi:10.21809/rilemtechlett.2017.52

Abstract

The analysis by microscopy of the compositions and microstructures of geomaterials found in historic structures and buildings is integral to archaeological, art-historical, conservation and restoration-related investigations, and supports decision making for material replacement and repair. In archaeology there is a need to elucidate past social, economic and technological processes, and to understand the environmental impacts of past human activities related to materials use. Standard light and electron microscopy are most commonly employed, but high resolution methods such as transmission electron and three-dimensional tomography such as µ-CT are also being used. Experimental and novel developments, where they overlap with advanced materials science, are uncommon. The application of scientific characterisation frames cultural heritage value, reinforcing our understanding of authenticity and integrity. Characterisation is constrained, in turn, by the values system that operates in cultural heritage. International charters and conservation philosophy necessitate the application of science to contextualising conservation. However, the appearance of science in heritage work has also led to the performance of science for its own sake (‘endoscience’, sensu Muñoz Viñas, Contemporary Theory of Conservation, Routledge, 2011). This moves some to suggest that there is a disconnect between scientific work and its practical value. Apparent communication problems between scientists applying microscopy and other stakeholders require changes to management of material characterisation in heritage projects.

Highlights

Scientific methods of material analysis are accepted, and often considered an essential, integral part of the conservation of heritage objects, buildings and sites
Microscopy, as applied to the characterisation of materials in historic structures will be used to consider the interaction of science with conservation
This paper focuses on geomaterials used for construction; stone, brick, concrete, ceramics and mortar, and does not reiterate its predecessors, but considers the place of analysis in active conservation

Summary

Introduction

Scientific methods of material analysis are accepted, and often considered an essential, integral part of the conservation of heritage objects, buildings and sites. Characterisation defines condition and allows the diagnosis of agents of change, the factors that cause deterioration, and can clarify necessary courses of conservation intervention It in this context, defines the historic fabric and reinforces the authenticity and integrity of the heritage ‘asset’, by the sheer force of the knowledge about the material reality of the object or building [1]. Microscopy has been extensively applied to the characterisation of mortars from historic buildings ([15] for an earlier review), and is included in most standardised analysis protocols [30] This is done for several reasons, most often not related to condition or damage diagnosis. Microscopy allows for clear and transferable visual characterisation of the materials, which through publication serve as a resource to other analysts faced with similar materials situations

Analysis in support of conservation interventions

Archaeological characterisation

Summary of applications and uses of microscopy

Conclusion

Understanding the transport of nanolime consolidants within

International Charter for the Conservation and Restoration of