Frost on a window glass is essentially the same as the frost that formed on the ground and on the branches of trees. The mechanism of formation of frost and these patterns are the same.
If the air is cooled, it decreases the moisture content. Frost patterns on glass and needles of frost formed in the case, if moist air is cooled to the freezing point of water, i.e. to 0°C. At this temperature, there is condensation of excess moisture contained in the humid air on cold surfaces. When water crystallizes, that is, turns into tiny ice crystals. Thus, the water contained in the wet air at 0°C is transferred from the gaseous state to the solid (crystalline), bypassing the liquid phase.
Why do ice crystals form such bizarre forms? The cause bumps and scratches on the glass surface. They ice crystals are formed in the first place. The crystals are deposited one after the other, at each other - and get amazing unique patterns. In addition to the irregularities of the glass, in the "drawing" patterns are dust particles on the glass surface and air flow.
Among the diversity of frosty pattern is more commonly seen tree-like structures called dendrites and filamentous forms - Tricity.
Dendrites are formed, if the humidity is increased, and cooling the glass began at positive temperature and continued with further increasing temperature. In this case, the glass is first formed film of water which, when freezing crystallize in the form of dendrites. Often this process begins at the bottom of the glass, because under the influence of gravity accumulates more water. Therefore, in the lower part of the window glass dendrites are usually larger, and the higher the ice "twigs" thinner and smaller. If the glass is quenched by cooling evenly, that is covered with a more or less smooth film of water, the "branches" of the dendrites of approximately equal magnitude across the surface of the glass.
Frost - dendrites
If the glass is scratched, their sharp edges formed by the second type of patterns - Tricity. First formed narrow parallel crystal strips. Upon further cooling "painted" fiber extending from the main "stem". Often the "stem" and "fiber", off of it, not straight, but slightly curved.
Frost - Trinity
Is it possible to make it so that the frost does not appear on the window glass in winter? You!
We have already talked about the fact that the sine qua non of education frosty patterns is the increased moisture content in the air and a cold glass. If you exclude any of these factors, Santa Claus will not be able to decorate a window glass for his paintings.
For example, you can reduce the humidity of the air near the surface of the glass, then condensation of water on it will not occur. This can be put between the window glass glass with concentrated sulfuric acid is known that it absorbs moisture from the air.
The second way is to prevent the glass is strongly cooled. Do this by careful insulation of exterior window glass at the point of contact with the frame.