4. Conclusion

Traditional stone building was adapted to the world in which it flourished, but this environment has changed drastically over the last few centuries. Quarry depletion and falling transport costs, particularly by road, have led to the search for more distant quarries, offering materials of unproven compatibility. The sealing of soils generates more surface runoff, which can infiltrate buildings. These run-offs now potentially carry many "new" chemical species on the scale of historic buildings, such as bleach, de-icing salts, surfactants, nitrates of agricultural origin, sewage effluents...

What's more, the treatments currently used to clean or consolidate stone also bring their share of mechanical, hydric and chemical stresses, the effects of which are not always observable on the life scale of today's techniques or commercial products. Today's environment, in the...