Water purity and aggressiveness
Purer water is a stronger solvent, not a gentler one. It cleans metal better and etches carbonate stone, and both facts have the same cause.
In detail
Water dissolves things until it approaches equilibrium with them. Tap water already carries dissolved calcium, magnesium and carbonate, so it arrives at a surface part-loaded and has less capacity left. De-ionised or distilled water arrives empty and takes up whatever it can reach. Federal conservation guidance states both halves of the consequence in the same paragraph: de-ionised or distilled water is MORE AGGRESSIVE for cleaning than tap water and is recommended on bronze plaques for exactly that reason — and it must NOT be used for cleaning plaques mounted on polished stone, marble, limestone or concrete, because the water can cause slight surface etching. This reverses an intuition that runs through domestic cleaning advice, where distilled water is treated as the safe option because it leaves no water marks. It leaves no marks because it carries nothing, and it carries nothing because it has capacity to take something — which on a calcium carbonate surface is the stone itself. The practical rule is that purity is a property to match to the substrate rather than a virtue.
Why
- Water is explained by Water purity and aggressiveness
- Architectural bronze is explained by Water purity and aggressiveness
- Polished marble is explained by Water purity and aggressiveness
- Limestone is explained by Water purity and aggressiveness
- Concrete and stone paving is explained by Water purity and aggressiveness
- Outdoors is explained by Water purity and aggressiveness
Sources for this page
Sources
Conserve O Gram 10/5: Caring for Outdoor Bronze Plaques, Part II — Cleaning and Waxing
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That de-ionised or distilled water is more aggressive for cleaning than tap water and recommended on bronze plaques, and that it should not be used on plaques mounted on highly polished stone, marble, limestone or concrete as the water can cause slight surface etching. (states this directly)
Verification: a person has read the passage relied on.
Read on — 'Introduction to Cleaning and Waxing', 'Preparation', 'Cleaning' and 'Waxing'. Supports the claim as stated. Supplies a complete outdoor metal cleaning system with required aftercare, and one fact with much wider reach than its subject: distilled water is more aggressive than tap water and etches carbonate stone.
Last reviewed by a person on .