Acorn Crew: Frost, Nature's Fingerprints

By Clara Wodny on December 19, 2024 in Blog

You wake up on a chilly winter morning and look out the window to find the ground, your car and other surfaces covered in tiny, sparkling ice crystals. What you’re noticing is frost — the frozen counterpart to dewdrops.

The Formation of Frost

Frost forms through a process called deposition, when water vapor that is suspended in the air cools enough to condensate and turn into liquid. If the surface that the water vapor condensates on top of is cold enough, it will skip the liquid state and immediately transform into ice, becoming frost. Because heat rises, the air near the ground is typically much cooler. If the surface on which the water vapor condensates is below freezing, it is possible for frost to form even if the overall air temperature is above freezing.

Types of Frost

Not all frost is created equal. There are many varieties, differentiated based on where and how they form.

Hoarfrost, also known as radiation frost, is the most common. Hoarfrost occurs when water vapor directly freezes into ice crystals upon touching a cold, exposed surface. In addition to commonly coating sidewalks, grass and car surfaces, the frost that forms inside of your refrigerator and freezer is likely hoarfrost.

Advection frost refers to tiny spikes of ice that form when very cold air blows into an area and replaces warm air. It is usually associated with cloudy conditions and strong winds, forming on surfaces like tree branches and metal poles.

A third type of frost, called rime frost, forms quickly in very cold, wet or windy climates. Rime frost particles tend to be thicker and sturdier than hoarfrost, which means it can last up to several days and build up over time. True hoarfrost is much more delicate and will not build up over time. 

Make Your Own Frost!

You can closely observe the process of frost forming inside the comfort of your home—all you need is a can or jar with a lid, ice cubes and salt. Fill the can or jar with ice, then add several spoonfulls of salt — which lowers the melting point of ice — causing the surface of the jar to fall below freezing. This allows frost to form indoors in a generally warm environment. Finally, put the lid on and shake vigorously, until the surface of the can feels very cold and a unique frost pattern begins to form.

Nature’s Decorations

Frost is one of nature’s many phenomena that helps transform the outside world into a captivating, breathtaking winter wonderland. Next time you’re salting your sidewalk or scraping frost off your car’s windshield, take a moment to appreciate the uniqueness of each crystal and nature’s ability to constantly create something new.