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Tired of tea scum? How to banish it for ever – and make the perfect cuppa

Name: Tea scum.

Age: Literally ancient.

Appearance: A grotty, cuppa-topping oil slick.

Is this some sort of horrible slur? No, not at all. Although “tea scum” may sound like something that a violent coffee enthusiast may spray paint on the front door of someone who prefers PG Tips, we’re talking about the actual thing.

What actual thing? You make a cup of tea and let it sit for a few minutes, only to be confronted by a grotesque waxy film on the surface when you bring it up to your mouth.

Oh yes, that. I always put that down to my partner stirring my tea with a dirty spoon because they hate me. Fortunately, that is not the case. Your partner may hate you, but it has been revealed that tea scum is caused by a simple chemical process.

Really? Clearly you don’t read the scientific journal the Physics of Fluids, because that’s all anyone there can talk about.

Fine then, talk me through it. Scientists at the Institute of Food, Nutrition and Health in Zurich, discovered that tea leaves contain compounds called polyphenols. These have a habit of bonding with calcium carbonate in tap water. And when this happens, a film tends to appear at the surface of the tea cup.

That’s disgusting. No, it isn’t. The film is flavourless and harmless to consume. The worst thing it does is slightly hinder the tea’s aroma. Unless you are an intolerable aesthete, you have nothing to worry about.

But I am an intolerable aesthete! It’s still not the end of the world. Scientists have discovered ways to mitigate the forming of the film.

Please tell me, immediately. Well, you could add a drop of lemon juice to your tea, since this was discovered to produce a thinner film of scum. Alternatively, start drinking Earl Grey, because the acidity of bergamot rinds in the blend has the same effect.

Done. Also, you may want to consider moving house.

Pardon? The biggest factor that influences tea scum is the hardness of the water. Areas where tap water contains more dissolved minerals – such as the south-east of England and most of Ireland – give the polyphenols more to bond with, which leads to more scum. But tea drinkers in soft-water areas such as the West Country, Wales, the north-west and Scotland will find much less scum.

Fine, I’ll move! Also, drink your tea black. Milk makes the scum worse.

What am I, a monster? I’d rather drown in tea scum than drink black tea. Suit yourself.

Do say: “If you want a decent cup of tea, move to Cornwall.”

Don’t say: “Especially if you’re moving from London. The locals love that.”