What Makes Ice Slippery?

It might seem a silly question at first, but when stepping back and considering why ice is so slick, and poses such a hazard to us bipedal hominids in the form of slip-and-fall injuries, the answer is more nuanced and surprising than we initially think.

By Eric Herman

As winter’s cold tightens its grip on most of the Northern Hemisphere, leaving many landscapes and bodies of water cover in ice, I thought it might be interesting to look at the basic question of what exactly makes ice so slippery.

To most of us, the answer is simply that’s just the way it is, how nature intended it. Water turns to liquid at zero degrees Celsius and below that it becomes an ultra-smooth solid. We know that above freezing liquid water is viscous, but that still doesn’t explain how ice below freezing air temperatures is slippery.

After all, if it’s frozen, there should be no slippery liquid water on the ice surface. And, when you look at ice on a microscopic level, it’s made of sharp geometric crystals that are anything but smooth. The slipperiness of ice is actually counterintuitive.

Icy Interface Zone

As it turns out, the physical science of frozen water offers a fascinating explanation, one that’s still being explored.

It started more than 150 years ago when legendary physicist Michael Faraday, the visionary who discovered the principles of electromagnetism, also discovered that at temperatures below 0 *C, there exists a thin film of water that is not quite liquid, nor solid. He, in effect, found an aqueous lubricant on the surface of ice that makes figure skating, hockey and bobsledding possible.

Faraday’s discovery has since fueled volumes of scientific inquiry from scientists the world over, and has even led to controversy and pointed debate among many. Some of the questions studied and argued have included at what temperature below freezing does this quasi-liquid layer of water form? Is it’s thickness dependent on temperature? In what manner does thickness increase as temperature rises? Does it form continuously or stepwise?

Ice’s slippery nature has, indeed, intrigued scientists for centuries, because it often behaves in ways that defy simple intuition. Early explanations posited that pressure exerted by a skate blade or a foot caused localized melting of the surface, producing a thin film of liquid water that acted as a lubricant.

Contemporary studies in physical chemistry and surface physics emphasize the importance of the unique molecular properties of ice surfaces. Research published in The Journal of Physical Chemistry Letters shows that ice’s surface features a highly mobile layer of water molecules even below the freezing point, which facilitates sliding. In this premelting regime, the thermal motion of loosely-bound molecules on the outermost layer creates a slippery interface, and friction is correlated with this enhanced mobility rather than simply with bulk melting from pressure or heat.

This molecular mobility mirrors a quasi-liquid layer that persists even at temperatures well below 0 °C. Further complicating the picture, very recent studies (e.g., 2025 research from Saarland University) propose that the slipperiness may additionally derive from molecular dipole interactions at the surface: when another material touches the ice, the electrical interactions between dipoles in the contact surface and those in the ice disrupt the ordered crystal structure, generating a disordered, liquid-like layer on the surface that significantly reduces friction.

This work challenges the long-standing pressure-melting/friction explanations and suggests the slipperiness can occur even at extremely low temperatures where melting is thermodynamically unlikely.

Faraday was Right

As Faraday discovered, ice’s slipperiness arises from its remarkable surface physics, where highly mobile molecules and even molecular dipole interactions create conditions of extremely low friction. Understanding this helps not just in appreciating the science behind winter phenomena, but also in applying practical strategies to stay safe.

Whether navigating a treacherous sidewalk or driving on a freezing highway, prioritizing traction, reducing speed, and paying attention to conditions can meaningfully lower the risk of falls and accidents in icy conditions.

A December 12, 2016 article published by Science Daily, covering a presentation on this very subject at the National Academy of Science, revealed that at 0 *C, right before liquid water forms, this enigmatic layer grows to 45 nanometers thick. That is 1/1000^th the thickness of a human hair. In effect, this layer which is responsible for the slippery nature of ice is, at its thickest, not even visible to the naked eye.

A new study by scientists at the Max Plank Institute for Polymer Research — working with a multi-national team of researchers, using advanced spectroscopy and computer modeling — conclusively discovered that at the molecular level, the quasi-liquid layer begins to form at -38 *C. However, contrary to popular belief that ice melts continuously as temperatures rise, the research also revealed that at -16 *C, a separate layer begins to form.

The conclusion ice is slippery not because ice is inherently “slippery” as a material, but because at the molecular level its surface behaves in a unique way. Rather than being static and rigid like many solids, ice’s uppermost layer is dynamic and facilitates sliding with very low friction when in contact with other materials, whether that be a skate blade, shoe sole, or tire tread.

Walking Safely on Ice

The slippery nature of ice is far from purely theoretical, it’s a characteristic that has direct impact on our world, and particularly our ability to safely move around in it when it’s covered with ice.

Walking on icy surfaces poses a significant hazard because the low friction at the ice–shoe interface makes it hard to maintain stability and balance. Simple precautions can dramatically reduce the risk of slips and falls:

Wear appropriate footwear: Choose boots or shoes with non-slip soles and good traction (rubber or neoprene composites) rather than smooth leather or hard plastics, which are more prone to sliding.
Take smaller, cautious steps: Short, shuffle-style steps keep your center of gravity over your feet and minimize the sideways and forward forces that cause slips. This approach is often likened to “walking like a penguin.”
Look ahead and plan your path: Avoid stepping on glossy, wet-looking surfaces where ice might be present, and when possible, use cleared paths or areas treated with salt or grit.
Use supports: If handrails or solid supports are available, use them when navigating stairs or sloped surfaces.
Keep arms out of pockets: This can help you balance and react quickly in case of a slip.

Even with perfect preparation, ice can conceal hazards such as black ice—a transparent coating that blends almost seamlessly with pavement and is extremely hard to detect but highly slippery.

Driving Safely on Ice

Ice dramatically affects vehicle traction, increasing stopping distances and reducing steering control. These are some key evidence-based safety considerations:

Slow down and keep your distance: Reducing speed gives you more time to react and increases the chance your tires can maintain traction. Leaving extra space between vehicles is critical because stopping distances on ice are much longer than on dry pavement.
Avoid sudden maneuvers: Gentle steering and smooth braking help prevent skids. Hard or abrupt inputs often lead to loss of control on slick surfaces.
Mind visibility and road conditions: Low sun angles, freezing rain, or “flash freezes” (wet roads rapidly icing as temperatures drop) all make it vital to assume ice is present near freezing conditions and adjust accordingly.
Use proper tires or traction aids: Winter tires with deeper tread and softer rubber compounds provide better grip on ice than all-season tires. Devices such as snow chains or snow socks can also improve traction in severe conditions (though legality and practicality vary by region).
Prepare your vehicle: Ensuring your car is winter-ready with good battery health, correct tire pressure, and sufficient windshield fluid improves safety when ice or snow is present.

Where possible, the best safety measure on icy roads is to delay or avoid driving until conditions improve. Ice can form suddenly, especially in shaded areas like bridges and overpasses, and even cautious drivers can become vulnerable to unexpected low-traction patches.

Suffice to say, there’s more to ice than meets the eye!

Ice crystal image by Zorankrstic | Shutterstock