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I live in a hard-water area and find that vinegar is a cheap and effective way to descale my kettle. But no matter how much I rinse afterwards, I won’t get a decent cuppa for a week. Given that the kettle is stainless steel and plastic, why does the taint stay so long? A proprietary citric acid descaler presents no such problem, but is less effective and more expensive.

Robert Bull, Bath, Somerset, UK

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