Written by Paul Hetzler
posted on January 13, 2019 12:42
When the thermometer starts dipping into negative values at night, and only rises into the single digits in the day, the morning may come when our car, smart phone, water pipes, fingers and/or other essentials have frozen and refuse to work. It’s easy to get so “frosted” by winter’s hardships that we miss its artistry. Given the right conditions, though, winter frost can transform the world overnight, with a breathtaking majesty that would melt any heart.
Naturally, we tend to associate frost with the “bookends” of winter, when the seasons are changing. The frosted lawn in April or October is neither unusual nor very interesting, at least not without a hand lens to see better detail. But mid-winter frost, while not as common, can be truly extravagant.
The kind of frost that turns any landscape into a winter magic-land is called hoarfrost, “hoar” being Old English for grizzled. Hoarfrost occurs in supersaturated conditions when the relative humidity is more than 100%. This may sound like an impossibility, but in fact it’s common, at least for short periods of time.
Photo courtesy Chris Murray
Warm air can hold much more water vapor than cold air, so as the temperature falls in a humid air mass, relative humidity increases, eventually exceeding 100%. Supersaturated water vapor is an unstable condition, and nature is keen to restore balance by shedding moisture. On a cool summer evening that would be in the form of dew, and on a frigid winter night it’s hoar frost.
Those fortunate enough to live in the Thousand Islands region are treated to hoarfrost often, as the open water provides necessary water vapor. On occasion, weather fronts can spread moisture, and thus hoarfrost, over a wide area.
In great literature and children’s stories alike, the theme of redemptive transformation is both compelling and appealing. Cinderella’s Fairy Godmother changed a pumpkin into a stagecoach, and mice into fine horses. She has nothing on hoarfrost, however, which I think must have learned its craft from the angels themselves.
As water vapor condenses onto cold surfaces, it applies layer upon crystalline layer of fragile, feathery, exquisite ice forms. Even the most ordinary and neglected objects—the weed patch, the tangle of rusty barbed wire—are redeemed by hoarfrost’s magic wand. But given a medium that’s more complex, more inherently eye-pleasing such as a tree branch, the effect is all the more inspiring. When that effect is multiplied, along fencerows and riverbanks, illuminated by morning sun, one has the urge to kneel on the spot and put a hand to one’s heart.
You can make ersatz hoarfrost by gathering together cold temperatures, water vapor and a substrate on which to collect ice crystals. The first is easy—we have plenty of cold these days. Water vapor, which can be an uncovered stockpot of water fresh off the wood stove, needs to be concentrated in an unheated garage, enclosed porch or outbuilding. By definition, every object is a substrate, but more intricate objects result in more elaborate crystal formations.
Photo courtesy Chris Murray
This might have to wait if you first need that pot of boiling water to thaw out those water pipes, in the crawl space, under your kitchen. While doing so, please keep in mind that “hoarfrost” is not an expletive.
By Paul Hetzler
Paul Hetzler is a Horticulture and Natural Resources Educator at Cornell Cooperative Extension, in Canton, NY. He writes a series of humorous and informative essays for a number of newspapers and journals. Subjects range from trees, gardens, insects, native plants, water, wildlife and other natural resources topics. Paul is also the author of "Shady Characters," a collection of humorous nature essays and the unique website “Where the Wild Words Are” – check it out!