A conservation cleaning method that uses a very fine, low-pressure mist of water to soften water-soluble dirt and deposits on stone.
Nebulous spray cleaning, also called intermittent mist spraying, is a conservation method in which a very fine, low-pressure mist of water is directed onto stone or masonry. The aim is to soften water-soluble dirt and encrustations while using substantially less water than conventional washing.
The method is valued for delicate historic stone because the impact on the surface is minimal and the amount and duration of wetting can be closely controlled. It must nevertheless be used cautiously, since excessive moisture can mobilize salts, corrode hidden metal, or damage friable material.
Etymology
From Latin nebula, “mist” or “cloud”; the conservation term refers to the mist-like spray produced by fine nozzles.
Sculptor Notes
This is primarily a conservation method rather than a carving method. On historic sculpture, the goal is not to make stone look new but to remove harmful or obscuring deposits without erasing tool marks, patina, softened detail, or other evidence of age.
References
https://www.pierres-info.fr/glossaire/index.html; https://www.buildingconservation.com/articles/nebulous/nebulous.htm