Children who live in places where the winters get cold love to see frost on the windows. Some of the patterns are quite beautiful and look like intricate designs on trees or leaves.
For this frost to form on the window panes as well as on trees and grass-certain conditions are necessary. Frost is made up of tiny crystals of frozen water. It forms when air that has a lot of moisture in it is cooled below the freezing temperature of water.
This temperature, which we call the freezing point, is 32 degrees Fahrenheit and zero degrees centigrade, at sea level. When the air becomes cooler, it cannot hold as much water as before.
The excess water condenses on such objects as the windowpane. Now, if the temperature falls below 32 degrees Fahrenheit, this water becomes crystallized. In other words, it freezes into a coating of interlocked crystals of water.
What causes the patterns to appear in the frost on the windowpanes? For one thing, the tiny crystals have a certain structure which gives them a pattern. In addition, there may be tiny scratches in the glass, dust particles, air currents-all of which help create the designs that “Jack Frost” makes on your windows.
White frost, which is often called hoarfrost, is of two kinds, granular and crystalline. Granular frost is simply frozen fog. The crystalline frost, which we have described, is formed directly from the water vapor in the air. It goes right from being a gas to being a solid, without going through the liquid state.
Frost, as you know, can be a serious danger for the farmer by killing buds or ripening fruit. Actually, it is not the frost itself, but the freezing of the plant juices that is harmful. So farmers have had to develop ways of preventing frost to save their crops.
One way is to cover the plants with a light cloth to prevent radiation of heat. Smudge pots in orchards cover the trees with thick smoke, and this also helps the plants hold in their heat. So while you enjoy seeing the work of “Jack Frost” remember that it may mean serious damage to millions of pounds worth of crops.