The short answer
Cover the scale in white vinegar or citric acid solution, leave it an hour, and rinse thoroughly. It dissolves without any scrubbing at all.
- Kettle: fill to halfway with equal parts white vinegar and water, bring almost to the boil, switch off and leave for an hour.
- Shower head: unscrew it if you can and stand it in a bowl of the same mixture. If you cannot, fill a food bag with the solution, tie it over the head with a rubber band and leave it overnight.
- Iron: fill with a weak citric acid solution, steam it through into a sink, then run two tanks of plain water through to flush it.
- Rinse three times. This is the step people skip and it is why the next cup of tea tastes of chips.
What will ruin it
Vinegar will damage the rubber seals and aluminium parts inside some kettles and irons over time. Citric acid powder, sold cheaply for exactly this, is gentler and has no smell. Check the manual for anything expensive.
Why it works
Limescale is calcium carbonate deposited out of hard water when it is heated. Acid turns it into calcium salts that dissolve, so it leaves in the rinse water rather than needing to be scraped.
Household chemicals can be dangerous in combination. Never mix them, keep the room ventilated, and test anything on a hidden patch first. Full disclaimer.
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