Water hardness
Dissolved calcium and magnesium picked up from the ground. It decides how much detergent you need, what your kettle looks like inside, and whether surfaces dry clean.
In detail
Hard water is water carrying dissolved calcium and magnesium compounds, acquired as rain percolates through carbonate rock, which is why hardness is a property of geology rather than of plumbing and varies sharply between neighbouring regions. Three consequences follow, and they look unrelated until the cause is named. Hardness ions react with soaps and interfere with surfactants, so more detergent is needed to achieve the same effect — which is what laundry builders and chelating agents are added to formulations to address. Heating hard water drives dissolved calcium bicarbonate out of solution as insoluble calcium carbonate, which is limescale, and explains why scale forms on heating elements and inside kettles far faster than on cold surfaces. And hard water evaporating in place leaves its mineral content behind as a visible film, which is why water marks are a hard-water problem and why rinsing with clean water and then drying actively is the trade recommendation rather than a fastidious extra. The practical point is that hardness is worth knowing about your own supply, because it converts three recurring annoyances into one explanation with one set of answers.
Why
- Descaling is explained by Water hardness
- Rinsing and drying is explained by Water hardness
- Limescale is explained by Water hardness
- Water marks is explained by Water hardness
- Sunscreen is explained by Water hardness
The unusual case: hard water normally leaves a deposit you can see. Here it supplies the iron that turns an invisible residue into an orange stain.
- Stainless steel is explained by Water hardness
Sources for this page
Sources
Care and Maintenance of Stainless Steel
British Stainless Steel Association, Stainless Steel Advisory Service, 2001 · Trade or professional body
Relied on for: That adherent hard water scales form on stainless steel and are treated with acid, and that clean potable rinsing water and active drying avoid water marking. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 re-read all four pages: Factors Affecting Maintenance, Maintenance Programme, Cleaning Methods with the whole of Table 1, Table 2, and Notes 1-10. Earlier sprints named both tables but carried only part of one and none of the notes. Supports a wider statement — our claim was widened. SPRINT 29 FOUND THIS UNDER-EXTRACTED WHILE ALL THREE SIGNALS CALLED IT DONE: zero representation debt, in the fully-harvested list, and honestly noted as 'read in full'. Five of Table 1's eleven rows, all of Table 2 and eight of ten notes had never reached the graph. Newly built: tannin and coffee deposits, heat discolouration, the 1% ammonia routine clearance, oxalic acid for embedded iron, and the condition-triggered domestic frequency rule. The paraphrase cap is part of the cause, and the fix is not a longer paraphrase — the facts belong in the citing records.
Handbook of Detergents (Surfactant Science Series)
CRC Press / Taylor & Francis · Reference work
Relied on for: That water hardness arises from dissolved calcium and magnesium, reduces detergency through interaction with surfactants, and is addressed by builders and chelants. (background and mechanism only)
Verification: the work exists and is described correctly. Nobody has yet read the specific passage.
Last reviewed by a person on .