Deadwood Candyfloss in Winter
Hair Ice: a Special Feature of the Sihlwald
On windless, cold winter days, hair ice forms: a phenomenon that regularly occurs in the Sihlwald natural forest.
In the cold winter months, filigree, candyfloss-like formations known as "hair ice" or "frost beard" can be found on dead trees and branches left lying around in the Sihlwald forest. It consists of fine, hair-like ice crystals that are often less than a tenth of a millimeter in diameter and are correspondingly fragile.
Hair grows on fungus-infested wood
Hair ice grows exclusively on dead hardwood that has been colonized by the fungus Exidiopsis effusa. This fungus remains active even in winter and breaks down the nutrients present in the wood. The resulting gases displace the liquid water in the wood, which is forced out through the wood pores and freezes into fine threads of ice just below the freezing point. As water continuously flows out of the wood, the ice grows continuously and forms the characteristic hairy structure.
Frost beard only under ideal conditions
This rare natural phenomenon is only visible in very specific weather conditions: hair ice forms overnight and usually only lasts for a short time. Cold, snowless and, above all, windless winter days are crucial, as even a light wind destroys the fragile formations. Haareis can therefore often be found in shady, wind-protected hollows – always close to the ground, directly on the damp, fungus-infested dead wood from which it grows.
