The deranged knee: restoration of function

Salt weathering is a major cause of deterioration of buildings and monuments of cultural heritage. We have determined the underlaying moisture and ion transport within a representative building material by measuring the time evolution of NaCl-saturated samples during one-sided drying using nuclear magnetic resonance. The measured NaCl concentration profiles reflect the competition between advection to the surface and redistribution by diffusion. By representing the measured moisture and NaCl profiles in an efflorescence pathway diagram (EPD) the crystallization is also taken into account. The pathways followed in the EPD indicate that for historical objects in general, crystallization at the surface cannot be avoided.