Tag: vaporization

Lava Meets Leidenfrost
Drop water on a surface much hotter than its boiling point, and the liquid will bead up and skitter over the surface, levitated on a cushion of its own vapor. In addition to making the drop hypermobile, this vapor layer insulates it from the heat of the surface, allowing it to survive longer than it would at lower temperatures. Known as the Leidenfrost effect, this phenomenon can show up in lava flows, as well.
Pillow lava is a smooth, bulbous rock formed when lava breaks out underwater. The exiting lava is incandescent and, therefore, incredibly hot — hot enough to vaporize a layer of water surrounding it. The lava can continue to expand until it cools too much to sustain the vapor layer. An elastic skin builds up over the cooling lava. Eventually, a new pillow will bud off, possibly due to a surge in the lava flow or a weak point in the developing skin. (Image credit: J. de Gier; research credit: A. Mills; via LeidenForce)
Fediverse Reactions
July 17, 2025
Exciting a Flame in a Trough
A viewer sent Steve Mould his accidental discovery of this odd flame behavior. In these 3D-printed troughs, a flame lit in lighter fluid will rocket around the track repeatedly as it burns the local supply of gaseous lighter fluid. As Steve shows in his video, this system is an excitable medium and the trick works for a whole array of 3D-printed shapes. Check out the full video above. (Video and image credit: S. Mould)
May 20, 2024
Leidenfrost Collapse
When a droplet encounters a surface much hotter than its boiling point, it forms a thin layer of vapor that insulates the liquid from the surface. But this Leidenfrost effect can’t last forever. Eventually, the vapor layer destabilizes and the drop touches the surface, causing explosive boiling that destroys the drop.
To determine how the layer destabilizes, researchers simulated the breakdown. To their surprise, they found that inertial forces in the micron-thin vapor layer were critical for destabilization. The gas inertia caused reductions in pressure that pulled the liquid toward the surface. Usually at these small scales, we’d ignore inertial effects and focus instead on viscosity, but, for Leidenfrost drops, that simplification doesn’t work. (Image credit: L. Gledhill; research credit: D. Harvey and J. Burton)
November 6, 2023
Leidenfrost Explosion
When a water drop hits a surface that’s much hotter than its boiling point, part of it will vaporize immediately. Depending on the temperature, this Leidenfrost effect can be a relatively gentle process — or not. Here, the surface is so hot that the entire drop is boiling before it’s even finished spreading from impact. The vapor in contact with the surface is trying to escape, bubbling up so violently that it rips the original droplet into a spray of tiny droplets. (Video and image credit: L. Gledhill)
March 8, 2023
How Fabric Dries
How do damp clothes dry in air? Such a seemingly simple question has vexed physicists for years because it’s extremely difficult to observe what happens inside the cloth fibers. Now researchers have used magnetic resonance techniques to track the material’s drying process.
Inside wet fabric, water exists in one of two states: it can be bound to the fabric fibers through hydrogen bonds or it circulates as a vapor in the voids between. Before this study, scientists had no way of confirming the relationship between these two states. Models simply assumed that most of the drying took place as water vapor left the fabric.
In their measurements, the team watched textiles dry in open-topped containers exposed to dry air. With their magnetic resonance technique, they could track the bound water in the textile over time. They found that the model that fit their data the best is one in which the bound water and water vapor reach equilibrium instantaneously. (Image credit: K. Cao; research credit: X. Ma et al.; via APS Physics; submitted by Kam-Yung Soh)
May 10, 2022
Triple Leidenfrost Effect
Droplets can skitter across a hot surface on a layer of their own vapor, thanks to the Leidenfrost effect. If two Leidenfrost droplets of the same liquid collide, they merge immediately. But that doesn’t always happen with two dissimilar liquids. A new study looks at how dissimilar Leidenfrost droplets collide. The researchers found that these drops can bounce off one another repeatedly before their eventual merger (Image 1).
Just as a vapor layer prevents the drops from touching the hot plate, a vapor layer forms between them when they collide, preventing contact (Image 2). Because of these three distinct areas of Leidenfrost vapor (one beneath each drop and one between the drops), the researchers call this the triple Leidenfrost effect.
Eventually, the more volatile (in other words, easily evaporated) drop shrinks to a size similar to its capillary length, at which point the drops merge. If the boiling points of the two liquids are vastly different, the merger can be explosive (Image 3). (Image and research credit: F. Pacheco-Vázquez et al.; via APS Physics)
December 16, 2021
Digging Droplets
A droplet on a surface much hotter than its boiling point will skate on a layer of its own vapor, thanks to the Leidenfrost effect. But if that surface is, instead, a granular mixture like this glass powder, the droplet will dig itself a hole.
As in the usual Leidenfrost situation, the heat of the powder causes part of the drop to vaporize. But as that vapor flows away, it carries powder with it. At the same time, the vaporization process causes the droplet to vibrate violently, which frees more powder and helps the drop dig deeper. Eventually, the drop will vaporize completely, leaving a volcano-like crater in the powder. (Image and video credit: C. Kalelkar and H. Sai)
September 3, 2020
Molten Thermite
This glowing, molten liquid captured by the Slow Mo Guys is thermite. The chemical reaction behind thermite is highly exothermic, hence its intense glow. There’s some great fluid dynamics hiding in this video. First, there’s the dripping thermite (Image 1), which breaks up into droplets via the Plateau-Rayleigh instability before shattering when it hits the ground.
Then there are the sequences (Images 2 and 3) of thermite dripping into water. The heat of the reacting thermite vaporizes a layer of water around it, creating a bubble that completely envelops the thermite. In other words, the falling thermite is supercavitating! That layer of air significantly reduces drag on the thermite and it insulates the thermite from the cooler temperature of the water. (Video and image credit: The Slow Mo Guys)
August 18, 2020
The Explosive Vaporization Derby
When pressurized, liquids can be superheated to temperatures well above their normal boiling point. When the pressure is released, the liquid will start boiling, sometimes explosively. In this video, researchers explore that dynamic by “racing” a series of liquids against one another. Each racer has been heated to a different temperature beyond the expected boiling point.
The clear winner is the liquid with the highest overheat; as explained in the latter part of the video, beyond a critical overheat temperature, vaporization waves in the fluid enhance the boiling, helping vaporization take place faster. (Video and image credit: K. Jing et al.)
August 12, 2020
Drops That Dig
On extremely hot surfaces, droplets will skitter on a layer of their own vapor, thanks to the Leidenfrost effect. This keeps the liquid insulated from contact with the hot surface. But what if the surface isn’t solid?
That situation is what we see above. Instead of soaking into a granular material like a room temperature droplet (left), a drop falling onto a very hot bed of grains digs a hole! As with a typical drop on a super hot surface, the heat vaporizes part of the droplet. As the vapor escapes, it carries sand with it, allowing the boiling drop to burrow its way into the material. As the temperature difference between the sand and droplet changes, the digging slows. Eventually, the drop comes to a rest and boils away. (Video and image credit: J. Zou et al.)
November 8, 2019