What Makes Frost Form On Windows?

In order for frost to form on a window, the outside pane must be exposed to freezing temperatures. Warm moist air seeps from inside the house to form moisture on the outside pane which then freezes into the designs we see. With the coming of double paned windows, frosty windows aren't as common as it used to be years ago when the windows were a single pane, covered by a storm window on the outside. This type of old window leaked a lot of warm moist air from inside the house where it accumulated on the outside storm window and froze.

A squeeky clean window will only produce a more solid sheet of frost that looks more like sleet than frost. In order for the frost to form the common leaf-like design, a few streaks need to be present on the pane. This slightly soiled streak is necessary. It gives the frost a starting point, something to cling to. The frost usually starts forming at the outside edge of the window, then it will follow along the streak, whichever direction the streak goes. In an effort to produce different patterns in the frost, I frequently rearranged the streaks on the glass on sunny days when the frost melted and the glass was clear of frost. Notice the different patterns that were produced by doing this. The rising sun was used for background color in many of the pictures. Others have a clear blue sky as the background and still others, only snow or an overcast sky.

I hope you enjoyed the pictures. Thanks for looking.
kosssuth