Why does everything look so turbulent right up until it’s dry?


Why does everything look so turbulent right up until it’s dry?


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About the Author: livescience

15 Comments

  1. My guess is that the glitter stays moving because the liquid is evaporating off, and its not really moving all that much.

  2. Movements in the liquid suspension cause the glitter to reflect light in different ways, stops when enough of the liquid evaporates leaving behind the glitter that was suspended in it

  3. Brownian motion exaggerated by the fact we view reflected light so small changes in angle look like larger movements.

  4. Watching it sped up you can see it keeps moving in the direction of the stroke after it calms down as it dries until it’s completely settled.

    I guess I’m surprised that there’s so much motion in what I’d expect to be a pretty still liquid.

  5. It’s just displaying the Brownian motion that exists in all fluids. A cup of water moves similarly, too.

  6. There’s something named the Marangoni Effect/Flow which describes how if a liquid dropet (or in this case a line) is evaporating, material will need to move from the centre toward the edges, leading to circulation as shown [here](https://www.sciencedirect.com/science/article/pii/S0021979720313977). This is why coffee stains will have a thick border as more material is deposited at the edges. I’d imagine that is at least partially responsible for all the movement, and the glitter is helping a lot by making it much more obvious.

  7. Evaporation causes convection currents in droplets, adding to the Brownian motion of the flakes.

    I believe we’re seeing the mechanism that forms coffee rings, but the size of the flakes doesn’t allow for a concentration gradient like you see with coffee.

  8. maybe it’s heated from below?

    edit: I noticed some movement to the right as it dries, maybe it has warm air blowing on it?

  9. Assuming it’s alcohol-based ink, it’s literally boiling away. The liquid evaporates, leaving only the pigment behind, stuck to the paper

    Idk how other ink types work but it’s assume they work the same

  10. This is so cool. It looks like a weld beads slap solidifying behind the puddle.

    Edit, slag not slap.

  11. Brownian motion I would guess.

    Once it’s dry Brownian motion is not strong enough to allow the particles to move anymore.

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