People living and working in areas with hard water have a constant battle on their hands when it comes to making a decent cuppa.

Many of us use filters to soften the water and take away impurities, but there is a good reason not to bother.

According to the experts, counter-intuitively, unfiltered tea tastes better! Swiss scientists based at ETH Zurich (what a shame they’re not from Yorkshire) have studied how chemical impurities in tap water can make tea taste better. Water that comes from limestone aquifers contains calcium carbonate which, according to science, gives the water a ‘crisper’ taste.

You can tell when you’re in a hard water area as the impurities in the water cause a thin film to form on the surface of your tea, which is especially noticeable before you put the milk in. You do not get this film when you use pure water, and while it looks better, it’s not such a good thing for the taste which becomes bitter.

The Swiss scientists explained: “There are many factors that affect the formation of this film, but the primary one is calcium carbonate in the water. When tap water contains a high amount of minerals such as calcium carbonate, it is called hard water.”

The science of tea

While the limescale in parts of the UK improves the taste of a good old brew in this country, things are different in other parts of the world. Chinese scientists have come up with the best water type to maximise the taste of their favourite teas, but also the antioxidant qualities too. For example, when it comes to green, oolong and black tea, purified water and mountain spring water are said to be better in terms of taste and antioxidant capacity.

There’s even a scientific reason behind the age-old debate about whether to put the milk in first or second. Dr Andrew Stapley, chemical engineer and member of the Royal Society of Chemistry, advised the BBC a few years ago that it’s best to put the milk in first: "At high temperatures, milk proteins - which are normally all curled up foetus-like - begin to unfold and link together in clumps.

This is what happens in UHT (ultra-heat-treated milk and is why it doesn't taste as good as fresh milk.” When the tea is added to the milk, the milk cools the tea. When the milk is added to the tea, the heat is more likely to result in a "denaturation of milk proteins" which can spoil the milk.

Who knew making a cuppa could be so complex!

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