Salt conversion, backfilling, and back anchoring: the securing of the painted ceiling of the Red Hall in the Neues Museum, Berlin (original) (raw)
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Sodium chloride crystallization in a “salt transporting” restoration plaster
2006
In recent years several types of restoration plasters, especially developed for salt loaded substrates, have been introduced on the market. The behaviour of these plasters in the field is, however, not always satisfactory. The reasons for failures may be found both in the moisture and salt transport behaviour of the substrate/plaster combination and in the severity of the situation (salt load, moisture supply and environmental conditions). In the present paper a restoration plaster for salt loaded substrates is examined. Its properties and composition are investigated in laboratory by means of multiple techniques (MIP, PFM, ESEM, XRD and FTIR). Particular attention is given to the study of the salt (NaCl) crystallization in the plaster. Field situations are considered in which this plaster shows damage after a few years from its application. The knowledge of the specific situation, together with the information gained in the laboratory research on the plaster, explains the fast development of the decay.
Water and Chloride Transport Properties of Renovation Plasters Developed for Historical Masonry
2011
Water and water-soluble salts represent harmful substances that critically affect materials’ durability and service life. Therefore, for the durability improvement of buildings, it is necessary to study water and salt transport properties of materials used in the building structures. Especially in historical buildings, several degradation mechanisms of water and water soluble salts can be usually recognized. On that account, investigation of properties of two types of newly developed mortars that should find application in restoration of masonry of historical buildings is presented in the paper. Within the performed experiments, measurements of chloride binding isotherms, moisture and salt concentration profiles are done. Determination of moisture and chloride concentration profiles is done in the conditions of one-sided water or sodium-chloride-in-water solution uptake. Experimentally determined concentration profiles are then used for identification of chloride diffusion coefficie...
Crystallization of salts is recognized as a major factor in the degradation of porous materials in built heritage. Salt damage occurs in the presence of salts and moisture, in liquid or vapour form. This implies that, in case one of both can be excluded, salt damage can be mitigated. A salt extraction aims to reduce a maximum amount of salts present. In practice salt extractions are often executed without scientific background or control of its effect or durability.This paper deals with the results of salt extractions using a poultice consisting of a mixture of kaolin, sand and cellulose fibers applied on salt contaminated brickwork of two cases, the abandoned coal mine site named C-mine in Winterslag and two chapels of the Cathedral of Our Lady in Antwerp. Results have shown that several factors influence the salt extraction effect: the amount and distribution of salts, the prewetting properties, the physical properties of the building materials as well as the environmental conditions of the salt extraction execution. From the experimentally determined salt contamination and distribution as well as the properties of the poultice and the building materials of the masonry, the salt extraction execution parameters and its effect were first approached theoretically through modelling. The predicted effect was compared to the one experimentally determined. Concerning the last, powder drill samples were lifted from brick and mortar, before and after each salt extraction from which the ion content was determined quantitatively. From the results it was concluded that the optimum conditions for the execution of a salt extraction cannot be considered as a standard copy-paste application suitable for all types of salt contaminated brickwork. A critical note is to be tackled with respect to the term "salt extraction" as the reality shows that an important part of the salts migrate deeper into the brickwork.
Microstructure of renovation plasters and their resistance to salt
Construction and Building Materials, 2018
h i g h l i g h t s Durability of renovation plasters. The resistance to salt crystallization. Intensity of salts solutions. Destructive effects of salts solutions. Plasters with low porosity and monomodal pore size distribution.
Transport and Crystallisation of Salts in Masonry and Plasters
2004
For the understanding of the salt crystallisation mechanism in restoration plasters, insight in the mechanism of moisture transport is essential, as well as in the influence of salts on that mechanism. More specifically the drying behaviour, i.e. the moisture / salt transport and distribution during drying, is important. For a number of damage cases the salt and moisture distribution is analysed and, for some of the cases, the development of the damage over time is shown. The same is done for damage development in laboratory experiments. Recent experiments with NMR make it possible to understand better the moisture transport and the drying of porous materials. On the basis of the discussed examples, hypotheses are proposed on factors determining the salt damage mechanism.
XIth International Conference on the Study and Conservation of Earthen Architectural Heritage, Terra, Peru, 2012
The Theban Necropolis on the West Bank of Luxor, Egypt preserves one of the world’s richest repositories of ancient painted tombs, including those in the Valley of the Kings and the Valley of the Queens. Over three millennia, many tombs have been subjected to flooding, causing severe rock collapse and loss of surface decoration. How best to conserve and repair vulnerable wall painting in the tombs is an urgent issue. Understanding the nature and composition of original materials is necessary in the selection of appropriate treatments for stabilizing fragile painted plasters. As a result, investigation of Egyptian plasters became a focus of study as part of the ongoing Queens Valley collaborative project between Egypt’s Supreme Council of Antiquities (SCA) and the Getty Conservation Institute (GCI). Based on a review of the literature, it was clear that the binder and aggregate composition of Egyptian plasters is not well understood. Despite a generally accepted belief that plasters were bound with gypsum and clay, past and current treatment approaches have relied primarily on lime-based repairs, poorly matched to the properties of original plasters. During recent episodes of flooding, the presence of such repairs has caused more harm to wall paintings, where differential stress reactions have led to cracking and loss in the weaker ancient plasters. This study allowed for characterization, investigation and analysis of a wide range of New Kingdom period tomb plasters from the Valley of the Queens in order to clarify many unresolved issues concerning binder and aggregate types and ratios. Findings indicated that the ancient craftsmen had an empirically informed understanding of the properties and uses of gypsum and clay binders in mortars and plasters. In particular, the role of clay as a binder appears to be far more widespread and nuanced than previously recognized, and the stabilizing role of calcite in plasters has been largely overlooked. These results have fundamental implications for improving the formulation of repair plasters for stabilizing wall paintings. The development of compatible repair plasters is therefore a key outcome of this project.
Effect of coatings on moisture and salt transfer phenomena of plasters
Construction and Building Materials, 2013
ABSTRACT For the protection of masonries against salt dampness various plasters and coatings are proposed. In many cases the application of inappropriate materials accelerates the degradation process. In this work the performance of different types of premixed plasters, suitable for confronting rising damp problems, along with different coatings (silane-siloxane coating and potassium silicate paint) were evaluated. For this purpose water vapour transmission rate experiments for uncoated and coated plaster were performed. Moreover, in order to investigate the durability to salt decay, an ageing test, through repeated cycles of capillary absorption of sodium sulphate solution, on brick-plaster-coating systems was carried out. The ageing test was monitored with the aid of infrared thermography. The results showed that the applied coatings seem not to influence moisture and salt transfer phenomena. Moreover, the plasters which presented the ability to transport the salt solution from the brick substrate, assuring the brick durability, are preferable in respect to salt transport blocking plasters. (C) 2013 Published by Elsevier Ltd.
Environmental Earth Sciences 63: 1487-1509, 2011
El Paular Monastery (eleventh century) is one of the most important Carthusian monasteries in Spain and is highly affected by crystallisation of Mg-sulphates, together with chlorides and nitrates. Urgent remediation of the decay process is needed to guarantee the stability of the building materials from the cloister and to make their hallways suitable for the exhibition of an important collection of seventeenth century paintings. This paper aims to characterise the building materials, salts and their interaction to suggest preservation strategies to minimise the impact of salts both in the short and the long term. These strategies include architectural solutions (such as a ventilation system to avoid increasing dampness and hence the dissolution, mobilisation and crystallisation of salts), petrophysical-based solutions (i.e. exploiting the porosity differences between building materials and poultices to maximise salt reduction) and strategies based on the physicochemical behaviour of salts and relative humidity transfer through the stone (to determine the most suitable environmental conditions to prevent crystallisation of the most harmful salt species). This research represents both a practical and experimental exercise that is useful for conservation scientists and restorers involved in the field of preservation of monuments, and for environmental control to avoid salt crystallisation.