Godts, Sebastiaan; Orr, Scott; Stahlbuhk, Amelie; Desarnaud, Julie; De Clercq, Hilde; De Kock, Tim; Cnudde, Veerle; Godts, Sebastiaan; Orr, Scott; Stahlbuhk, Amelie; Desarnaud, Julie; De Clercq, Hilde; De Kock, Tim; Cnudde, Veerle; Steiger, Michael; - view fewer (2025) Salt mixture mysteries: strategies for conservation. In: Proceedings of the 15th International Congress on the Deterioration and Conservation of Stone. : Paris, France. (In press).

Text Stone2025_paper_Godts-etal final.pdf - Accepted Version Access restricted to UCL open access staff until 26 November 2025. Download (730kB)

Abstract

Deterioration of porous materials in heritage buildings is widespread and often caused by the presence of salt mixtures. In this contribution we summarize the results of 11,412 samples from 338 heritage sites analysed to better understand and mitigate such deterioration. Using this set of samples and by enhancing methodologies for interpreting salt mixtures, common multi-ion systems were identified. Recognizing these mixtures allows more accurate predictions of their crystallisation–dissolution behaviour and impact on material degradation. Advanced techniques, including Environmental Scanning Electron Microscopy, Dynamic Vapor Sorption, time-lapse micrographs under changing relative humidity RH, Raman Spectroscopy, and X-ray Diffraction, were employed to closely examine how salts evolve with changing RH. Thermodynamic modelling via ECOS/RUNSALT further explained the equilibrium crystallisation sequences of multiion salts under various RH ranges, offering valuable insights for preventive conservation. However, kinetic delays, supersaturation and delayed nucleation, commonly shift crystallisation well below the model’s equilibrium predictions, emphasizing that model outputs must be contextualized with empirical data. To highlight the practical relevance, this research includes a case study of an artwork colloquially referred to as the “Salt Chair,” demonstrating how a predominantly halite-based crust with minor impurities can partially dissolve at RH values lower than expected, creating “logged-out” salt solution under seemingly stable indoor conditions. The study concludes that controlling both equilibrium thresholds and rates of RH change is critical in reducing salt-induced deterioration in heritage contexts.

Download activity - last month

Export as XMLCSVJSON

Download activity - last 12 months

Export as CSVXMLJSON

Downloads by country - last 12 months

Export as JSONCSVXML

Archive Staff Only

View Item