Users of cameras and eyeglasses will be familiar with the phenomenon of fogging, which occurs when one goes from a cold and dry place into a warm one. This occurs because air can hold about 7% more water per unit of volume for each ËšC of additional temperature. That means that air in warm places is naturally more laden with water than that in cold ones. When the water-laden air hits cool glass, it condenses into a fog that confounds the bespecktacled and shutterbugs.
The other night, I witnessed a special elaboration of this phenomenon unique to conditions including (a) a very cold and dry night (b) a fairly large volume of glass and (c) an instant transition to a warm and relatively humid coffee shop.
The normal fogging occurred, but it would not dissipate after several minutes of waiting. It was then that I noticed that the glass on which the fog had formed was cold enough to freeze it – leaving a thin sheet of ice of the lens. The remedy was a few minutes of huffing to melt the ice, followed by a few more waiting for evaporation.
I am a bit surprised not to have experienced this working with cameras in Finland or Estonia. Like getting mild frostbite walking home from a party, it seems to be an Ottawa experience.