While making tea last night I forgot all about it and left the kitchen. When I did remember about it, I ran back and I was surprised to see that it was still in the vessel (though it formed a peculiar foam-like mass on the top).

boiling tea

This pushed me to do the same with water and milk (as these were constituents this tea).

I was not so lucky in case of milk, When I boiled the milk it rose too much and overflowed.


Boiling water alone didn't help either. The level of water in the vessel rose a little but it was far from overflowing (I provided the highest temperature as I could provide to vessel).


So I observed three different phenomena for three different liquids:

  1. Tea (having water and milk in proportion of 3 and 1) rose till the height of container.

  2. Milk overflows.

  3. Water doesn't even remotely show anything that would indicate it was responsible for this peculiar behaviour of tea.

I can't seem to figure out why this happens. Would anyone know why?Thanks for any help


After listning to people saying that they need more experimental data I decided to go further.

I boiled the milk along with water in a proportion of 1 by 1 (without tea leaves and sugar to it) and did the same with different proportions of milk and water.

After doing so I got that As I increased the amount of water (in combo of milk and water) the level of solution started decreasing and ultimately at the ratio of 1 and 5 (for milk and water) the solution didn't overflow.

The results were as expected but I thought these can be helpful for you guys in answering the question.

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    $\begingroup$ Related: Why does milk overflow when boiled? $\endgroup$
    – user7951
    Nov 1, 2016 at 11:54
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    $\begingroup$ You rightly mention that milk and water are components of tea. But perhaps I should direct your attention to the fact that they aren't the only components of tea. (There is of course, the powdered tea leaves you stir in) $\endgroup$ Nov 1, 2016 at 14:37
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    $\begingroup$ -_- Do I detect an undertone of sarcasm? $\endgroup$ Nov 1, 2016 at 14:47
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    $\begingroup$ What I implied, is that the powdered tea leaves clump together at the surface, forming that mass on top of the tea. This of course, wouldn't happen if you tried using a certain device we call a tea bag ;) $\endgroup$ Nov 1, 2016 at 14:51
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    $\begingroup$ Thought this was a lame question at first but because of the effort the OP put in with the photos it along with the response became quite interesting. Thanks for the effort. ps do the suggested experiments and report back. $\endgroup$ Nov 3, 2016 at 15:10

1 Answer 1


Original Hypothesis

As mentioned in this post, milk will overflow thanks to the effect of surfactants, which allow for the formation of stable bubbles. Since tea contains both milk and water, it contains surfactants from the milk, but at a lower concentration thanks to the water. This would result in some bubble formation, but not as much as you would find in pure milk, explaining why the tea filled up the container, but did not overflow. Either it was a coincidence that the bubbling stopped right at the top of the container, or it relates to the fact that more surface tension is required to create bubbles without the support of the container walls. In addition, other components in the tea could be contributing to this effect, but I think it is a result of the fact that milk and water are mixed. If you want to experiment with this, I would try a different volume of your water/milk mixture and see if that also makes it to the top of the container without overflowing.

Results of Additional Experiments

The results of your additional experiments seem to indicate that something else is going on. It is interesting that you found a different ratio that filled the container when there was no tea involved. This seems to indicate that the tea is at least somewhat involved in this interaction. Also, the fact that past the ratio of 1:5 (milk:water) the container did not fill up with bubbles seems to indicate that my hypothesis about surface tension was wrong, and that there is nothing special about filling the container. In this case, you probably just got lucky that your original tea did not overflow.

These results are dependent on the fact that you used the same vessel for your new experiments and allowed adequate time for bubbles to form. More information on your experimental procedures will help me narrow down on a possible explanation.

  • $\begingroup$ I have updated my question by adding new info to it.Hoping for a better answer. $\endgroup$ Nov 5, 2016 at 11:19
  • $\begingroup$ Did you preform these experiments in the same vessel? If so, it is somewhat surprising that the first milk:water ratio to not cause overflow was 1:5 while it was 1:3 with the tea. I will look into this more if it is the case. Also, did the 1:5 ratio stop right at the top of the vessel? If so, did a ratio like 1:6 also stop at the top, or did that just fill partway? $\endgroup$ Nov 5, 2016 at 16:57
  • $\begingroup$ Ratio of 1:5 reached too the top but as i started decreasing amount of milk,the height of solution get lower and lower $\endgroup$ Nov 5, 2016 at 17:11
  • $\begingroup$ @THELONEWOLF. I added additional information based off of your experimental procedure. I can narrow down on an explanation if you could write down more details about your procedure. $\endgroup$ Nov 5, 2016 at 21:16

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