If you are a person who lives in a country like the United States, Russia, Canada, Germany, Ireland, or Sweden, you may have faced the phenomenon that I am going to explain now. If you walk through a forest on a cold morning, if you are lucky, you’ll be able to see some shiny white cotton candy-like thing remain on the branches of trees. This thing is actually called “hair ice”. This is sometimes called ice wool in the forest. Actually, this is a very strange sight and it always fascinates humans who are lucky to come across them!

                To see these hair ice, the best chance is to have a hike into a broadleaf forest in a country between the latitudes of 45° and 55° N. Fungus are some special species in the world. They cause some weird things that happen around us. For example, some of them help humans to get rid of bed bugs. Some of them are deadly for bats and snakes. Some of them control insects. Here is something new to add to this list. Fungus creates a strange but amazing kind of ice called ‘hair ice’. Yes, a fungus species is the creator of this amazing hair ice.

Hair ice found in Skåne County, Sweden. By Lars Odemark

Below freezing temperatures, ice crystals are formed, and then they are ‘sculpted’ later as strands of hair by fungus. When there is water in the wood, they become freeze and act as a barrier and traps water between the ice and the wood. This creates a force of suction and pushes water from the pores of the wood to the edge of ice surface. Then that water freezes and extends outwards. This thin ice hair has a diameter of around 0.01 mm. These amazing things can be disappeared quickly with the sunrise or a human touch.

                This phenomenon was first discovered more than 100 years ago. In 1918, Alfred Wegener, the person who discovered continental drift made the first records about this hair ice. He identified some strange ice form appearing only on dead wet wood and he proposed a theory by saying that a specific fungus must be the reason for these smooth hairs of ice. He noticed that hair ice was only growing on lobs which had thin threads of fungus mycelium. So he thought there must be a relation between them.

Found near Rafford, Great Britain. By Des Colhoun

In 2015, the scientists called Matzler and Hofmann found the exact reason for the creation of this hair ice. They were from the Institute of Applied Physics at the University of Bern in Switzerland. They sampled logs and determined that one kind of fungus always showed up on the woods which grew hair ice. According to them, it happens because of a special fungus called Exidiopsis effusa.

They did experiments in a lab and found how this fungus form icy filaments.  When analyzing ice, they found few molecules in ice including lignin and tannin. They suspect that one of these molecules prevents ice crystals from growing large. But they still couldn’t confirm what molecules cause this phenomenon.


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