The Marangoni Effect

Final Project for the PHYS 379 Statistical Mechanics Class at St. Olaf College

[BarackBananabama]

I cried when I hear the botched music.

[payola]

This is, by far, the best video I've seen about this efect. Although, I have to confess I like the complicated sciency calculus part

[lynnzimmerman]

Nicely done! I've done a "Kaleidoscope of Milk" lab with my chemistry students (add food dyes to a Petri dish of whole milk, then touch the surface with a toothpick that has been dipped in soap) to see this effect. And now, I know what to call this phenomenon! Thanks!

[Xenochetemist]

Nice, I just saw Marangoni in the background of a meme.
Didn't know it's the name of this common effect.

4:45 Dividing by scale like this is an underused method I think. In the computational physics crowd it’s more common because there it is standard to “de-dimensionalize” your problem. It’s good to see the overall trend, but it’s also important to see whether there is a dependence on scale

[hund]

amazing video, i know, come 4 years late, but it really help me

[raywang]

Hi Kieran, this is great! I happen to observe some similar effect of oil film under water droplet during electrowetting, while the oil film forms a cross-section of a cut kiwi fruit. Wondering if you'd like to give a few comments?

[marcelmoura]

Wow, so cool! Good job :) Maybe this is connected to the physics behind the coffee ring effect too.

[karttikeya]

The radius of droplet initially increases with time in graph? Why? We saw it decreasing with time in the experiment.

[TaigiTWeseDiplomat--Formosan]

2:02 I noticed that when I take shower(water and soapy water) and now I know why.

[vaibhavparmar]

fascinating phenomena, I understand that water will flow outward but why in the form of small droplets? Sunflower oil and water also try to minimise the area of contact.

[nastybadger-tnkl]

Soap vs Water: The Real Surface Tension Story

🧪 Soap doesn’t "reduce" water’s surface tension — that's a misleading phrase.

⚡ Soap tries to dissolve itself into water instantly, triggering a violent interaction.

🌊 Soap is thicker (more viscous) and carries more internal energy than water.

💥 When soap hits water, it collapses the surface zone — not gently, but explosively.

🧲 This collapse forces nearby water to rush outward, creating the "pepper explosion" effect.

🌀 The spreading isn’t due to low tension — it’s due to soap’s high energy trying to balance itself.

🧼 Soap acts like a surface invader, consuming and replacing water molecules on the surface.

[.]

Same thing can be seen on the inside of wine glasses!

[ludolp]

Hello I tried to recreate this experiment but I had some troubles. Could you tell me how you did it?



The first problem I had was making the alcohol-water mixture visible (I was using isopropanol). I used basic food coloring you can find at the grocery store but for some reason you couldn't see it very well. What kind of food coloring did you use?

Secondly, how did you obtain your measurements of the mother droplet? I wouldn't know how to go about it in a practical way.

Thank you in advance.

[shineisland]

Interesting you referred to it as the mother droplet and little children. This is the answer to waters above waters below as well as the membrane between mother and child. That drawing you showed looks a lot like a placenta in the uterus 😉