# Peculiar phenomenon in tea made in a microwave - what is it? **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2024, 4:31pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929 "2024-12-20T16:31:19Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [December 20, 2024, 4:31pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/1 "2024-12-20T16:31:19Z")
When I heat up tea in a microwave and take it out, there is an irregular thin layer of foam, made of tiny tiny bubbles, of course. If I then slightly jiggle the mug, the foam arranges itself into parallel lines, sometimes 6 or 8 or more. If I then stir the foam it still often re-arranges itself into lines - usually fewer. I presume the lines are somehow a result of the action of the microwaves on the mug and the water, maybe something like sympathetic vibrations. But why would the phenomenon persist after I disturb the water? Is there some residual effect somehow? Minor vibrations in the ceramic mug? Any ideas, Dopers? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 20, 2024, 6:54pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/2 "2024-12-20T18:54:16Z")
Patterns like that, for example in a cup of coffee with cream added to it, can be a result of vortices in the circulating fluid. However, how are you preparing your tea so that a bunch of foam is extracted?? Or are we talking about only a few bubbles? Perhaps we need to merge this topic into this thread: [What's wrong with using a microwave to make tea?](https://boards.straightdope.com/t/whats-wrong-with-using-a-microwave-to-make-tea/1011513) ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [December 20, 2024, 7:30pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/3 "2024-12-20T19:30:49Z")
I don’t have an answer but I’d like to see a pic. I make tea in the microwave and have never experienced this. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [December 20, 2024, 8:00pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/4 "2024-12-20T20:00:06Z")
Not sure how to upload a photo, but I’m glad to provide an image. I put the water in the cup with a tea bag and nuke it for a minute. Not a whole lot of foam is produced, just a thin film. I’ll try to figure out the upload. ---
**Author:** ![Johnny\_Bravo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_bravo/32/493_2.png) [@Johnny\_Bravo](https://boards.straightdope.com/u/Johnny_Bravo)\ **Post date:** [December 20, 2024, 8:04pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/5 "2024-12-20T20:04:19Z")
Is it a clean mug every time, or might there be sugar or cream residue at the bottom? ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [December 20, 2024, 8:11pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/6 "2024-12-20T20:11:48Z")
Clean, out of the dishwasher. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [December 20, 2024, 8:49pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/7 "2024-12-20T20:49:46Z")
Maybe this will work. Looks like you’ll have to click on the image or the URL. [[Album] imgur.com ![](https://i.imgur.com/U84acW2.jpeg?fb "imgur.com") ](https://imgur.com/a/MirL21w) ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 20, 2024, 8:59pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/8 "2024-12-20T20:59:36Z")
That does not look so bad, though I would keep the teabag away from the water until the water is boiling. I am still thinking convection cells: > **[Rayleigh–Bénard convection](https://en.wikipedia.org/wiki/Rayleigh%E2%80%93B%C3%A9nard_convection)** > > In fluid thermodynamics, Rayleigh–Bénard convection is a type of natural convection, occurring in a planar horizontal layer of fluid heated from below, in which the fluid develops a regular pattern of convection cells known as Bénard cells. Such systems were first investigated by Joseph Valentin Boussinesq and Anton Oberbeck in the 19th century. This phenomenon can also manifest where a species denser than the electrolyte is consumed from below and generated at the top. Bénard–Rayleigh c Buoyancy... ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [December 20, 2024, 9:03pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/9 "2024-12-20T21:03:14Z")
> [@](#): > > Peculiar phenomenon in tea made in a microwave - what is it? It’s an appliance that heats things—but that’s not important right now. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [December 20, 2024, 9:23pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/10 "2024-12-20T21:23:54Z")
I don’t know…If the phenomenon is from the heating of the surface from below, why doesn’t it happen when the water is poured onto a teabag from a kettle? ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [December 20, 2024, 9:26pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/11 "2024-12-20T21:26:43Z")
Oh, bravo. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 21, 2024, 12:40am UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/12 "2024-12-21T00:40:02Z")
Do you get any of those little foamy bubbles when pouring hot water from a kettle onto a teabag? If not, then there would be nothing to make swirly patterns visible. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [December 21, 2024, 1:18am UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/13 "2024-12-21T01:18:03Z")
I suspect the foam is a result of the teabag contents or the teabag itself forming nucleation sites for bubbles. Heating in the microwave might be causing the dissolved air in the water to form bubbles on these sites, with some of the extractives from the tea stabilising the bubbles. And thus you get a foam that doesn’t appear on if you just pour hot water onto a tea bag. That the water is still whilst being uniformly heated is key. The preferential direction of the structure of the foam as it breaks down might simply be related to the direction the foam was pushed when the bag was taken out. Lines would form roughly parallel to the long axis of the tea bag as it sat in the water. You see similar patterns in sea foam. Although you stir the tea up, the foam is probably not fully broken up, rather just stretched and twisted, so there might remain some of the original structure that then spreads itself back out onto the surface once you are done. Spitballing ides so they are worth what you paid for them. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 21, 2024, 4:45pm UTC](https://boards.straightdope.com/t/peculiar-phenomenon-in-tea-made-in-a-microwave-what-is-it/1011929/14 "2024-12-21T16:45:07Z")
> [@CC](#): > > I don’t know…If the phenomenon is from the heating of the surface from below, why doesn’t it happen when the water is poured onto a teabag from a kettle? That behavior is mostly convection currents. Which are real weak & take time to form. While the water ischeating undisturbed in ghe microwave they have time to form. Contrast that with the much more violent agitation of the water being poured into the cup. By the time all that sloshing really settles down to stillness, the water will be cooling and what convection currents do form will be weaker. Any stirring you do further weakens the effects.