When glass has a temperature that is lower then, or equal to 0 degrees Celsius, any water coming in contact with it, will freeze and turn into ice. This is often seen in cold climates or seasons and might require the ice to be removed.
Why does ice form
When a vehicle is exposed to the environment, the temperature of that vehicle will change in the same way the environment does. In a heated garage, this means that the vehicle will absorb a lot of the heat from the air in the garage. When left outside, it will match the temperature of the air outside. This means it will get very warm in summer, and that same vehicle will be much cooler in winter. The temperature it will reach depends on the temperature of the air, and the speed at which the air moves. This is called “windchill” or “wind chill factor”. When the temperature of glass reaches 0 degrees Celsius or lower, water that will get in contact with this glass will freeze.
Frost is a coating of ice that forms in humid and/or cold conditions. Frost is composed of delicate branched patterns of ice crystals formed as the result of fractal process development. In certain situations, frost can form on surfaces which surface temperature is above 0 degrees Celsius.
The term “frost” is used when describing ice-like formation on surfaces without it having rained, or another form of water falling on the surface.
Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color. Ice molecules can exhibit up to sixteen different phases (packing geometries) that depend on temperature and pressure. When water is cooled rapidly (quenching), up to three different types of amorphous ice can form depending on the history of its pressure and temperature. The term “ice” is used when describing ice-like formation on surfaces after it has rained, or another form of water falling on the surface.
When air blows, the movement of air can give the impression that it is colder outside then a temperature gauge would say. A surface (like the windscreen of a car) that has a lot of cold air flowing over it, can become colder then the temperature of the air itself. This means the windscreen can become -1 degrees, even though the temperature gauge says it is 2 degrees outside. In this situation, ice or frost can form on your windscreen, even though the air temperature is higher then the freezing point of water. If the wind stops blowing, the ice or frost would melt again as the windscreen slowly warms up to the actual air temperature.
Why remove frost
When frost or ice appear on a windscreen, it can be difficult to look through. The ice that forms on glass is very rarely free of impurities, and very rarely has a smooth and flat surface. Contaminants in the water, air molecules and other substances can cause the frozen water to turn matte. Which means you can’t look through it, and in those rare cases where you can look through it, the uneven surface will distort the light, giving a slight funhouse mirror effect to your vision. Without being able to see your surroundings clearly, it is unsafe, unwise and sometimes even illegal to drive your vehicle on the road. Removing the frozen water from your windscreen, or melting it back into water will restore visibility.
Metal versus glass
Frost or ice can just as easily form on metal as on glass. However, both materials conduct heat (and cold) in different ways. Metal is a very good conductor of energy (electromagnetic radiation), and heat is energy. Cold can be simplified as the absence of that energy. When a piece of metal is placed inside a chamber where the air temperature is 2 degrees, the metal will quickly become 2 degrees as well. Glass is very bad at conducting energy, not only will it differ slightly per region, due to imperfections in the composition and stress of the glass, but it will also spread the difference in temperature very slowly. If one part of the glass is cooled down, it will very slowly pass that temperature difference the rest of the piece of the glass. This works the same for heating up. This causes glass to show frost or ice to form less quickly then on metallic body parts, but it will also require more effort/energy to melt that ice or frost once it has formed.