Etching versus staining
A stain sits on a surface and a mark from etching is a hole in it. They look similar, they need opposite responses, and cleaning harder makes one of them worse.
In detail
A stain is foreign material held on or in a surface: something arrived, and removing it means getting it out. Etching is the surface itself having been chemically removed: nothing arrived, and there is nothing to take away. On polished stone the two are easily confused because both appear as a mark that was not there yesterday, and the stone trade is careful to distinguish them — noting that some substances etch the finish without staining, others stain without etching, and some do both. The consequences of confusing them run in one direction only, which is why the distinction matters practically rather than academically. Treating a stain as a stain costs nothing. Treating an etch mark as a stain leads to progressively stronger cleaners and harder scrubbing applied to a surface that has nothing on it, which removes more surface. An etch mark is repaired by re-polishing, which is a refinishing job rather than a cleaning one. The test that usually settles it is texture rather than colour: run a fingertip across the boundary, because etching changes how the surface feels and a stain generally does not.
Why
- Polished marble is explained by Etching versus staining
Sources for this page
Sources
Care & Cleaning of Natural Stone
Natural Stone Institute · Trade or professional body
Relied on for: That some materials will etch the finish of stone without leaving a stain while others will both etch and stain, and that acidic substances dull or etch calcareous stone. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 read all nine sections. Earlier sprints had read three: the siliceous-versus-calcareous classification, cleaning products, and sealing. Supports a wider statement — our claim was widened. Three sections of nine had been read and the source treated as complete. The unread six carry the whole preventive programme - coasters, trivets, non-treated dry mopping, slip-resistant mats, worn vacuum wheels, blot-don't-wipe - none of which the register held. They also answer a priority-1 row reading 'no route answers this yet': the authority's position on etch marks is that they are not a cleaning problem and need professional re-polishing. Two oddities are worth the record: dry 0000 steel wool is permitted on water rings, and efflorescence is removed dry because water makes it worse.
Last reviewed by a person on .