The drive to work this morning was magical. There was a light fog that put everything in a soft-focus. Plus, vegetation was glistening with a delicate layer of hoar frost.
Hoar frost occurs when a winter fog coats the tree branches with a thin film of ice. This fog is a type of evaporation fog which results when cold air passes over water or warm, moist land. Evaporation increases the amount of moisture in the cool air, possibly to the point that the air can no longer hold all of the water it contains. And that is when the fog arrives.
The word hoar comes from an Old English word meaning "to look old." Since trees and other plants are covered in white by the frost, it was said that they looked old when covered with frost.
There are other types of frost that we see in winter. If you have ever lived in an old house, you have seen window frost (which some call fern frost because of the fern-like shapes it makes). Window frost forms on poorly insulated windows when it is cold outside and the air is moist inside - like it might be in the kitchen or bathroom.
When I was growing up, I loved to look at the window frost that would form on the panes of the window in my bathroom. The designs were beautiful. Little did I know that they were forming because the windows were letting all the warm air out (and the cold air in)!
I've seen window frost form inside a car when the warm air from the passengers' breath freezes on the windshield. This situation is usually quickly remedied by turning on the defroster and/or heater in the car. However, when I was first married and living in Vermont, my husband and I owned a '78 VW Beetle. It was a fun little car, but in the winter, it had virtually no heat. This meant that when we drove in it, our breath would freeze on the windshield, and there was no way to defrost it. That meant the driver would have to use a scrapper on the inside of the windshield to keep an area clear to see the road!
I don't recall spending any time admiring the fern-like patterns on the VW windshield!