Reigate Stone at the Tower of London

Studies in Conservation

Reigate stone was extensively used in medieval London and is prone to rapid decay. A variety of different conservation treatments has been applied in the past; in many cases, these have not mitigated ongoing decay. This paper presents an overview of wax, limewash, silane and ammonium tartrate treatment at the Tower of London and Hampton Court Palace. Documentary analysis and visual inspection indicate that whilst these methods have provided protection to some stones, no single method has resulted in the protection of all stones. Non-destructive and minimally-destructive testing is used to more closely assess the effects of ammonium tartrate treatment. The results imply that inherent stone mineralogy, past decay pathways and/or present environmental factors are a greater influence on ongoing decay than treatment histories.

2020

Reigate stone was extensively used in medieval London and is prone to rapid decay. A variety of different conservation treatments has been applied in the past; in many cases, these have not mitigated on-going decay. This paper presents an overview of wax, limewash, silane and ammonium tartrate treatment at the Tower of London and Hampton Court Palace. Documentary analysis and visual inspection indicate that whilst these methods have provided protection to some stones, no single method has resulted in the protection of all stones. Non-destructive and minimally-destructive testing is used to more closely assess the effects of ammonium tartrate treatment. The results imply that inherent stone mineralogy, past decay pathways and/or present environmental factors are a greater influence on ongoing decay than treatment histories. ARTICLE HISTORY Received June 2019 Accepted March 2020

Heritage Science

Reigate Stone was used in high profile projects across London during a key growth period and represents an important chapter of architectural heritage. Historic Reigate masonry is subject to inherent variability. It is prone to rapid decay; however, highly decayed and well-preserved stones are frequently adjacent. This inherent variability in masonry can present a challenge to the design of conservation strategies by obscuring or complicating the identification of decay processes. This paper presents a model for assessing the combined impact of construction economies and mineralogical variability (Graphical abstract), by synthesising archival research on the history of Reigate Stone with experimental analysis of its properties. The limitations of the local geography coupled with the demands of the medieval building industry are shown to have introduced inherent variability into the built fabric at an early stage. Later socioeconomic factors are shown to have compounded these by contributing to selective recycling, replacement and contamination of Reigate Stone. These historic factors augmented pre-existing mineralogical variability. This variability makes classification according to commonly used stone types difficult. Experimental analysis correlates variable cementing components with hygro-physical properties related to resilience. Calcite content influences strength properties and capillarity; clay content influences moisture adsorption and retention; opal-CT forms a weakly cemented, porous matrix. These presented different decay pathways to a range of environmental mechanisms and agents of decay. The findings suggest that inherent mineralogical variability, environmental changes, and historic contingency must all be considered in the design of ongoing Reigate Stone conservation strategies.

Minerals

The correct choice of pointing mortar is considered crucial to the conservation of historic masonry. A proliferation of cement and eminently hydraulic lime mortars since the late 19th century has accelerated the deterioration of built cultural heritage in many parts of the world. Whilst the use of softer, lime-based mortars in stone conservation is now common practice, their role in the overall conservation strategy of highly vulnerable building stones such as Reigate Stone requires assessment. In this paper non-destructive testing (NDT) is used across a two-year period to investigate the impact of different pointing mortar types in situ. NDT data on surface hardness and moisture are interpreted at different scales to assess moisture regulation of Reigate Stone masonry at the Wardrobe Tower, a ruined structure at the Tower of London, following repointing carried out in Spring 2017. Joints repointed using a hydraulic lime mortar (NHL3.5) are shown to regulate moisture in adjacent Rei...

Construction and Building Materials, 2015

Preliminary studies are an imperative when determining the impact of conservation treatments on historical materials. The Romanesque apse on a church at Talamanca de Jarama, Madrid, Spain, whose dolostone was severely decayed by rainwater and salts, was treated in the past with substances that ravaged the restored area. Petrological techniques showed that salts leached out of the cement under the roof onto the stone cornice whose surface had been coated with synthetic resins. During evaporation, the salts precipitated in the stone and underneath the resin, inducing blistering, fissuring, flaking, scaling and detachment of part of the restored decorative elements.

Journal of Cultural Heritage, 2015

Deterioration patterns are the visible consequences of the impact of environment factors on the stone objects. They depend on the type and severity of the external agents and on the type of substrate and its vulnerabilities. When properly understood, they may serve as key-indicators of the decay processes and of the possible causes of the observed damage. Correctly describing the deterioration patterns is an essential requisite when studying exposed stone objects, to understand the problems, to identify conservation needs and to define conservation actions. This paper discusses a few types of deterioration patterns to illustrate the need of choosing accurate definitions to describe them with the aim of reducing ambiguity when crossing the border between theory and practical application. The paper discusses a few deterioration patterns (detachment forms, black crusts and patina) that are currently found in conservation of built cultural heritage to highlight the importance of reducing the ambiguity that is frequently associated to such descriptive terms, aiming at better using them when acting in the passage from diagnostics to conservation actions. When mapping the spatial distribution of deterioration patterns, the most widely used methodologies are appropriate for scientific studies, but their usefulness to prepare and implement conservation interventions is much smaller. The paper proposes an innovative methodology to identify, describe and classify conservation problems and to prepare the documentation to support the tender documents in conservation interventions. A new methodology to help assessing the risk of structural instability and to help defining priorities in maintenance strategies in dry-stone laid constructions is presented.

2007

Geological Society books refereeing procedures The Society makes every effort to ensure that the scientific and production quality of its books matches that of its journals. Since 1997, all book proposals have been refereed by specialist reviewers as well as by the Society's Books Editorial Committee. If the referees identify weaknesses in the proposal, these must be addressed before the proposal is accepted. Once the book is accepted, the Society Book Editors ensure that the volume editors follow strict guidelines on refereeing and quality control. We insist that individual papers can only be accepted after satisfactory review by two independent referees. The questions on the review forms are similar to those for Journal of the Geological Society. The referees' forms and comments must be available to the Society's Book Editors on request. Although many of the books result from meetings, the editors are expected to commission papers that were not presented at the meeting to ensure that the book provides a balanced coverage of the subject. Being accepted for presentation at the meeting does not guarantee inclusion in the book. More information about submitting a proposal and producing a book for the Society can be found on its web site: www.geolsoc.org.uk.

Progress in Physical …, 2008

The problem of the decay and conservation of stone-built heritage is a complex one, requiring input across many disciplines to identify appropriate remedial steps and management strategies. Over the past few decades, earth scientists have brought a unique perspective to this challenging area, drawing on traditions and knowledge obtained from research into landscape development and the natural environment. This paper reviews the crucial themes that have arisen particularly, although not exclusively, from the work of physical geographers -themes that have sought to correct common misconceptions held by the public, as well as those directly engaged in construction and conservation, regarding the nature, causes and controls of building stone decay. It also looks to the future, suggesting how the behaviour of building stones (and hence the work of stone decay scientists) might alter in response to the looming challenge of climate change.

Atmosphere, 2020

The decay rates of building stones and, the processes leading to their deterioration is governed by intrinsic properties such as texture, mineralogy, porosity and pore size distribution, along with other extrinsic factors related to the climate and anthropogenic activities. For urban cities such as London, the influence of extrinsic factors like temperature and rainfall, as well as the concentrations of air pollutants, such as sulphur and nitrogen oxides, along with the emissions of carbonaceous aerosols, can be particularly significant. While considering the long-term preservation of building stones used in various heritage sites in the city, it is imperative to consider how the stone could be affected by the changing air pollutant concentrations, superimposed on the effects of climate change in the region, including rising average annual temperature and precipitation with a hotter, drier summer and, warmer, wetter winter months. This paper deals with the intrinsic rock properties ...

Construction & Building Materials 95: 611-622, 2015

Preliminary studies are an imperative when determining the impact of conservation treatments on historical materials. The Romanesque apse on a church at Talamanca de Jarama, Madrid, Spain, whose dolostone was severely decayed by rainwater and salts, was treated in the past with substances that ravaged the restored area. Petrological techniques showed that salts leached out of the cement under the roof onto the stone cornice whose surface had been coated with synthetic resins. During evaporation, the salts precipitated in the stone and underneath the resin, inducing blistering, fissuring, flaking, scaling and detachment of part of the restored decorative elements