A cooling hot drink

cup of tea

The current heatwave in England has had countless old wives, and a few elderly husbands, calling for a nice cup of tea to cool them down. And, when I say tea, I’m not talking none of that chilled variety that comes in peach and lemon and all sorts of other gawdy flavours, I mean a nice cup pored from a cosy-covered pot, with a splash of semi-skimmed milk and a couple of lumps of sugar (ten if you’re a builder or plumber, of course). So, what’s going on? Why drink a hot drink when it’s hot and you want to cool down.

Physically, it’s an illogical thing to do, Captain. Add something hot to a body at a lower temperature and the cooler body will absorb heat energy from that hot something and its temperature will rise, surely?

Physiologically, things might not be so clear-cut. Drink a hot drink, and yes, the temperature of your stomach’s contents will rise, but this will also cause a slight hastening of the heart, expanding blood vessels across the skin, and an increase in sweating as the brain switches on the various feedback-controlled temperature regulators.

It’s that word “feedback” that provides a possible clue as to why a cup of hot tea might have gained its reputation among English old wives as a good coolant. Feedback loops always have a time delay. So, the instant burst of heat that comes from sipping on a nice cup of tea will inevitably bring you out in a bit of a sweat, raise your heart rate etc, but those compensatory measures take time to be reversed, possibly more time than it takes for the contents of your gut to reach “body temperature” again. So, their cooling effect may just last a little longer than is actually needed to get you back to normal temperature and so you may end up a little cooler than when you started.

All that said, I don’t think our temperature feedback systems are that tardy. The real reason that old wives perceive a hot cup of tea to have a cooling effect is probably more to do with interrupting whatever activity it was that made them hot in the first place, partaking of the cup-of-tea creation ceremony, and sitting down in a darkened room with their feet up to drink it.

I could be wrong, and now that the storms are on their way this atypical English weather is likely to be replaced with the more usual wet and grey with which visitors become so familiar.

Now, where did I put those teabags…?

7 thoughts on “A cooling hot drink”

  1. responding to TDL
    Here in New England where the winter cold can periodically be brutal, it is a truism that hot water pipes freeze (and burst) before the cold water pipes. This is true despite the fact that hot and cold pipes run parallel and with (by most codes) no more than two inches between them.
    Whether the explanation is good or not I cannot say but I was told this is because the disparity in temp between the environment (or freezer) and the water is so much greater in the warm water that the dissipation of that heat energy creates a cascade effect, causing the hot water to reach environmental temp more rapidly than the cold water…which I guess, is lazy and feels like it has plenty of time. ??!!??!! Okay, I have my doubts, too.
    But finally, the question–Does hot water make ice cubes quicker than cold–is an easy enough experiment isn’t it–one tray of each in the freezer at the same time…

  2. I happened to work in an engineering firm where I was told that people working in forge shop use to take hot water to quench their thirst. I tried taking hot water to cold water during summer and I felt hot water was better than cold water.

  3. I remember seeing this on Tomorrows World, back in the 70’s, they had an infra red camera and all that, they proved that it was more cooling to drink and hot drink rather than a cold one. But I am sure they said something along the lines of, if you drink a cold drink the body needs to work to warm the contents of the stomach back up and this expelling of energy made you hotter. That obviously wouldnae explain why a hot drink cooled you down though. But it defo has to be T, coffee doesnae do the same thing, I’m no a big T drinker I prefer coffee, but on a hot day you can’t beat a cup of T.

  4. Hi Laura

    What is “colling” hot water? Perhaps you meant cooling. There are lots of simple experiments to do with the rate of cooling of water on the web. Have a closer look using Google and search for “cooling water experiment”.

  5. i am doing an experiment for year 8 science, i have to do some background research on my topic, i was wondering if you could help. My topic is colling hot water.

  6. Interesting.

    It reminded me of how frustrated I would get with the claim that it was faster to make ice cubes with hot water than with cold. Back then, I could only come up with one hypothesis as to why this might seem true–maybe if you put a tray of really hot water in your freezer, it tricks the thermostat to register a higher temperature and thus runs the compressor longer. It is possible that this feedback causes overall temperature to be colder for enough time to make the ice cubes freeze faster.

    In general, however, I just think the claim is wrong. :)


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