Knowra Salt weathering Salt weathering Salt weathering is the breakdown of porous stone as dissolved salts crystallize within its pores and exert pressure. Repeated crystallization and dissolution can loosen grains and detach flakes.
Crystallization pressure : Pressure generated when crystals grow against confining surfaces, potentially exceeding the strength of porous materials. Growing salt crystals can push against pore walls and detach mineral grains.
Porosity : The fraction of a material’s volume occupied by pores or voids. Salt weathering requires pore space that can admit and hold saline water.
Stone conservation : The assessment and treatment of stone objects and structures to slow deterioration while preserving their material and significance. Conservators diagnose salt damage before selecting cleaning, desalination, or moisture-control treatments.
Freeze–thaw weathering : Rock breakdown caused when water in pores freezes, expands, and stresses the surrounding material. Both processes exploit pore water, but freezing rather than crystal growth supplies the stress.
Halite : The mineral form of sodium chloride, commonly known as rock salt. Halite crystallization in pores is a familiar source of damage in arid and coastal settings.
Efflorescence : A deposit of salt crystals formed on a material’s exposed surface as saline moisture evaporates. Surface crystals mark salt transport, unlike damaging crystallization hidden within pores.
Capillary action : The movement of liquid through narrow spaces caused by surface tension and adhesion. Capillary flow carries dissolved salts into stone and toward evaporation zones.
Desalination (conservation) : The removal of soluble salts from porous cultural materials using methods such as poulticing or controlled washing. Desalination aims to reduce the salts that drive crystallization within historic stone.
Thermal stress weathering : Rock breakdown caused by stresses from heating, cooling, or temperature differences within a rock. Temperature-driven expansion can flake stone without requiring crystallizing salts.
Mirabilite : A hydrated sodium sulfate mineral with the formula Na₂SO₄·10H₂O. Sodium sulfate can cycle between hydrated and anhydrous forms, producing damaging stresses.
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