The poster shows a vivid collection of snow crystals photographed in the Austrian Alps using special equipment under artificial light.
Different snow crystals grow depending on the temperature and humidity.
- Between 0°C and -3°C, classic snowflakes (dendrites) form.
- Below -3°C, thin needles and hexagonal columns (prisms) grow.
- Between -10°C and -22°C, sector discs and aesthetic stars form again.
- Below -22°C, only prisms and flakes fall as snow.
- Below -40°C, no more crystals grow.
The crystals are always transparent. The colours visible here result from the recording technique using a microscope with LED backlighting.
Snow that falls to the ground is crystalline water, so it always consists of small crystals that form at sub-zero temperatures. At above-zero temperatures, the water vapour in air that is saturated with water vapour turns into liquid water, forming raindrops.
Both snow crystals and raindrops fall to the ground when they reach a certain size.
Spherical hailstones or sleet grains are formed when liquid raindrops freeze in a cloud when they enter a colder layer of air.
Snowflakes are on average about five millimetres in size and are either single crystals or clusters of several crystals.
The crystals are also transparent in nature. The white colour results from sunlight being reflected at many interfaces that are in a diffuse positional relationship to each other.
When snow lies on the ground for a long time, its structure changes repeatedly, even at sub-zero temperatures.
200g paper, lightfast, matt lacquer coating
