Külmavahtu

Külmavahtu is an Estonian term that translates to "cold foam" or "frost foam." It refers to a type of ice formation that occurs on cold surfaces, typically during freezing weather conditions. This phenomenon is most commonly observed in nature, such as on tree branches, fences, or window panes.

The formation of külmavahtu is a result of supercooled water droplets in the air coming into contact with a surface that is at or below the freezing point. When these droplets freeze upon contact, they create a layer of ice that can have a delicate, frothy appearance. The texture can vary, sometimes appearing as fine crystals and at other times as a more cohesive, foamy layer.

Külmavahtu is a transient phenomenon, often disappearing as temperatures rise or sunlight hits the affected surfaces. It is distinct from hoarfrost, which typically forms from water vapor deposition. While both are forms of ice, külmavahtu is a direct result of freezing liquid water droplets. It is an aesthetic aspect of winter weather, contributing to the visual landscape with its ethereal, icy formations. The term is used descriptively in Estonian to capture the specific visual quality of this type of frost.