Appearance is an incomplete diagnosis
A pale crust on stone can look like a housekeeping problem. Removing the visible deposit may leave the process that produced it untouched. In her conservation review, A. Elena Charola explains that deterioration reflects interactions among salts, moisture and a material's pores. Similar powdering or scaling can arise through different combinations of those conditions.
The useful question is therefore not simply whether salt is present. It is where the salts and moisture are moving and how that particular material responds.
Sources: s1
A modern example of added damage
National Park Service guidance on wildland-fire chemicals describes damage to heritage materials from discoloration, retained moisture and deposited salts. As moisture evaporates, salts can move toward a porous surface. Other changes can restrict moisture movement and contribute to flaking or crumbling. The guidance treats material identification and an appropriately gentle removal method as part of the problem, rather than assuming that every stain needs the same cleaning.
Sources: s2
Preserve the observation before the intervention
A treatment record needs a description of the material, location, visible alteration and environmental history before the intervention. 'Looks cleaner' is an appearance outcome; stability needs separate assessment. A meaningful comparison also needs a stated observation period and a way to detect continuing loss.
That distinction is useful for reading an excavation report or building a believable fictional ruin. A well-preserved object is not necessarily untouched, and a freshly cleaned surface is not necessarily secure. This page explains the diagnostic problem; it intentionally does not prescribe a chemical bath or a household restoration recipe.