Our shared cultural heritage comes in many forms and environments, not all of which are conducive to their long-term preservation. For example, salts are inevitably present in porous building materials like masonry, or natural limestone or sandstone walls. The way salts can migrate through these materials poses dangers to cultural heritage such as wall paintings. For example, salts can be drawn along with water and precipitate out in a bloom of salt on the surface (termed ‘efflorescence’), at interfaces (e.g. ‘blistering’ cement), or within a wall (‘subflorescence’). They can also host damaging bacteria that thrive in high levels of salt. Further complexity arises from the sensitivity of many salts naturally present in building materials to minute variations in environmental conditions. For example, sodium sulphate has two hydration states that both occur near room temperature, but which differ in volume by over 300%: the stresses induced by changes between these states suffices to shatter rocks! In this project, you will develop models of the physical and chemical processes giving rise to salt-induce damage to wall paintings and other cultural heritage. The aim of the work will be to predict when and where salts will appear for several buildings and sites operated by English Heritage, to inform their conservation efforts.
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