Adding tea to milk is not the same as adding milk to tea

Monday, September 23rd, 2019

Ronald Fisher was working at an agricultural research station north of London in the 1920s, when he fixed a cup of tea for an algae biologist named Muriel Bristol:

He knew she took milk with tea, so he poured some milk into a cup and added the tea to it.

That’s when the trouble started. Bristol refused the cup. “I won’t drink that,” she declared.

Fisher was taken aback. “Why?”

“Because you poured the milk into the cup first,” she said. She explained that she never drank tea unless the milk went in second.


“Surely,” Fisher reasoned with Bristol, “the order doesn’t matter.”

“It does,” she insisted. She even claimed she could taste the difference between tea brewed each way.

Fisher scoffed. “That’s impossible.”


“Let’s run a test,” [chemist William Roach] said. “We’ll make some tea each way and see if she can taste which cup is which.”

Bristol declared she was game. Fisher was also enthusiastic. But given his background designing experiments he wanted the test to be precise. He proposed making eight cups of tea, four milk-first and four tea-first. They’d present them to Bristol in random order and let her guess.


By the eighth cup Fisher was goggle-eyed behind his spectacles. Bristol had gotten every single one correct.

It turns out adding tea to milk is not the same as adding milk to tea, for chemical reasons. No one knew it at the time, but the fats and proteins in milk—which are hydrophobic, or water hating—can curl up and form little globules when milk mixes with water. In particular, when you pour milk into boiling hot tea, the first drops of milk that splash down get divided and isolated.

Surrounded by hot liquid, these isolated globules get scalded, and the whey proteins inside them—which unravel at around 160ºF—change shape and acquire a burnt-caramel flavor. (Ultra-high-temperature pasteurized milk, which is common in Europe, tastes funny to many Americans for a similar reason.) In contrast, pouring tea into milk prevents the isolation of globules, which minimizes scalding and the production of off-flavors.


Perhaps a little petulant, Fisher wondered whether Bristol had simply gotten lucky and guessed correctly all eight times. He worked out the math for this possibility and realized the odds were 1 in 70. So she probably could taste the difference.

But even then, he couldn’t stop thinking about the experiment. What if she’d made a mistake at some point? What if she’d switched two cups around, incorrectly identifying a tea-first cup as a milk-first cup and vice versa? He reran the numbers and found the odds of her guessing correctly in that case dropped from 1 in 70 to around 1 in 4. In other words, accurately identifying six of eight cups meant she could probably taste the difference, but he’d be much less confident in her ability—and he could quantify exactly how much less confident.

Furthermore, that lack of confidence told Fisher something: the sample size was too small. So he began running more numbers and found that 12 cups of tea, with 6 poured each way, would have been a better trial. An individual cup would carry less weight, so one data point wouldn’t skew things so much. Other variations of the experiment occurred to him as well (for example, using random numbers of tea-first and milk-first cups), and he explored these possibilities over the next few months.


Fisher published the fruit of his research in two seminal books, Statistical Methods for Research Workers and The Design of Experiments. The latter introduced several fundamental ideas, including the null hypothesis and statistical significance, that scientists worldwide still use today.


  1. Redan says:

    Evelyn Waugh:

    All nannies and many governesses, when pouring out tea, put the milk in first. (It is said by tea fanciers to produce a richer mixture.) Sharp children notice that this is not normally done in the drawing-room. To some this revelation becomes symbolic. We know a woman, far from conventional in other ways, who makes it her touchstone. “Rather m.i.f., darling,” she says to convey inferior social station.

  2. Graham says:

    I hadn’t realized this was another U vs non-U situation, so common over there.

    I had encountered the issue, but only as one of those vicious preferential wars that surround food and drink.

    Curiously, my mother’s habits and those of other relatives, all Scottish working class, were exclusively tea leaves or bag first, then pour water, then add milk and/or sugar. Clearly, this is how the universe desires these elements to be combined. And of those last two, milk first then sugar.

    But one has to get through all the disputes about milk vs no milk, sugar vs sweetener vs nothing, bag vs loose, loose in cup vs pot and strainer or tea ball, and so on.

    My parents can’t get away from tetley bags with too much milk and sugar. I can’t drink tea that way anymore. Depending on some long-undetermined variable of how much milk and what kind, and how much sugar, the resulting mixture can be pleasant or near gag-inducing, almost mucousy. Hard to believe this sort of thing once sustained an empire.

  3. Grasspunk says:

    It used to be: milk first is middle class, maybe more lower middle class who are showing off how they are more sophisticated than working class. See also fish knives and settees. Milk last is both upper middle and working class. The upper want the scalded taste to show how they have secret knowledge and the working class, well who knows the origin that’s just how my NZ colonial mother did it.

  4. Kirk says:

    It’s amazing how basic some things are, and yet which get ignored in seemingly important “science”. Good experiment design is critical, yet all too often, the experiment is poorly designed, and will not produce anything other than noise.

    What I’ve noticed in a lot of cases is that they seem to conduct the “experiment” first, and then go back and cherry-pick the results that support their initial thesis. Crap like that is all over “climate science”, and yet, none of the “peer reviewers” seem to take note of it all.

    I think that there needs to be an “Underwriters Laboratory” for a lot of this stuff; you need to have the research papers submitted to an independent third party that actually examines the work, looks at the design of the experiment, and then replicates the work independently. As it is, “peer review” basically means you’re asking the rest of the community to look at your work, and you all know that if they say something critical, you’ll criticize what they do later, and then all the grants will go somewhere else. So, what winds up happening is a mutually satisfactory circle-jerk where nobody’s work really gets questioned, unless there’s some money to be had doing it.

    Which, I think, is part of the reason that scientific progress has stalled; there’s too much consensus, and nobody is really looking at the unexpected outer edges of things. “Oh, no… Cold fusion can’t possibly be happening… That doesn’t conform with our understanding of the universe…”. Yeah. Well, maybe you don’t understand as much as you think you do…

    Not to argue for cold fusion, but that’s a point where I’m always going “OK, so… If it isn’t real, explain away these anomalies…”. Which, apparently, there are enough of to keep a bunch of people hacking away at the coal face. Not being a physics expert, I can’t evaluate whether they’re con artists wasting their time and ours, or actual pioneers of science. What I do know is that the rigid pipeline of consensus does not serve us well when we’ve gotten things fundamentally wrong.

  5. Graham says:


    Interesting. Another example of high and low against middle or, alternatively, aspirant middle classes picking the wrong horse when trying to appear elevated.

    If you look at the original lists of U or non-U words, there’s a lot of that. It’s not a perfect model, but the high aristocracy often actually uses the blunt, Saxon, or simple word where the aspiring classes use the more euphemistic, poseur French, or complicated term. Again, not perfect — the British aristocracy long used a lot of actual French and the royals at the top often speak it.

  6. Graham says:

    Cold Fusion can never work unless they put the milk in the reactor last.

  7. Alrenous says:

    The difference in taste is not subtle enough that you need to run blind trials. We also don’t need to run large clinical trials to determine the effects of beheading. It’s not ‘won’t drink that’ level, though; that’s normally being a snob for snobbery’s sake.

  8. CVLR says:

    Who mixes milk and tea?!

    (There’s probably an interesting paper to be written on who focuses on what: science or social.)

  9. Graham says:

    I gather that Russians (Russians!) once considered the English barbaric for adding milk to tea. Or wusses. Or both at once.

    Could be something in it.

    Ever the centrist, I add milk to the handful of teas where I think it taste appropriate- usually the basic bagged orange pekoe mixes that form the industrial base of the tea world. They get sweetened too. There may be other viable dairy candidates.

    I once saw someone add milk and sugar to Earl Grey. Hoooogh.

  10. Kirk says:

    The other point that’s glossed over, here, is that the person who objected to the flavor of the tea was female.

    It’s long been my observation that women, in general terms, are far more sensitive to things like flavor and smell than men are. I suspect that this is another one of those realities that the idiots are willing to ignore, in the belief that there is no difference between men and women. Things I find completely unobjectionable, in terms of scent and flavor? My female peers regard with horror…

    Not to mention, most women have low tolerance for environmental things, aesthetic issues that men don’t even notice. Friend of mine repainted the interior of his house with what was supposed to be the same shade his wife had picked out before her vacation. For some reason, the guy mixing it down at the paint store didn’t get it quite “right”, and his wife spotted it within seconds of getting home. None of the males involved could make it out, but she sure as hell could, along with three other women. They went down to the paint store in legion, and by the time they got done brow-beating the poor bastard managing the place, they had new paint and a professional paid to come apply it. Me? I could see no difference before, during, or after that fiasco, but the ladies could. And, apparently, some bizarre electronic spectrum analyzer that one of them had for her graphics design work–I remember one of them saying something to the effect that the first paint applied by the husband was a “…whole two pantone shades out…”, and we’re all going “Huh?”.

    Women are generally more sensitive to these things. Men may notice them, but we just kind of gloss over it all–The tea tastes “about right…”, and that’s all it takes. For her, though? “It ain’t right…”, and that’s all it takes.

    There’s probably something there in the evolutionary biology of it all, what with women having done rather more of the gathering bit of “hunter-gatherer”…

  11. Graham says:

    I remember appreciating the women’s skill set and habits when we needed them to sort out the good berries from the bad ones.

    Now I’m like- IS there another wall colour than Apartment White?

  12. Lucklucky says:

    Argh! milk? leave my tea alone!

  13. Alistair says:


    Women are feeding their children and possibly also their pregnant selves. These entities are less robust to poisoning to men. It would be completely sensible to expect women to be more sensitive to colour and odor or taste than men.

  14. Paul from Canada says:

    RE: Milk first or second also has class implications in the past.

    Apparently, lower classes had cheaper cups made of a different material than the upper classes (porcelain vs. bone china or whatever, I don’t remember the exact details).

    The cheaper cups could not handle the thermal shock of being cooled by having the milk put in first, and then the hot tea, so milk first was upper class. Something like that.

  15. George Henderson says:

    My missus has progressed to only tolerating UHT milk in tea, because it has that ready-scalded taste.
    Even though she’s m.i.s. because m.i.f. doesn’t make sense with a tea bag – you won’t get a proper draw.
    And if anything is déclassé it’s using a tea bag.
    Orwell, surely the only authority worth appealing to, is m.i.s. and no cream, but accepts that there exists a plurality of opinion on the issue in every British home.

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