Imagine wandering through the woods and finding across a white wig strewn across the road. It turns out, however, that it is not a wig when you touch it. Meet the one-of-a-kind “hair ice.”
Hair ice is a sort of ice that forms on dead wood and resembles fine, silky hair in appearance. This natural occurrence, also known as ice wool or frost beard, is rather unusual, occurring predominantly in broadleaf forests at latitudes between 45 and 55 °N.
When temperatures are just below 0 °C (32 °F) and the air is humid, this peculiar type of ice forms on moist, rotting wood from broadleaf trees. Hairs with a diameter of about 0.02 mm (0.0008 in) and a length of up to 20 cm are smooth and silky (8 in). Despite the fact that individual hairs are fragile, they frequently curl and wave.
Surprisingly, they may keep their shape for hours, if not days, at a time. Because re crystallization generally occurs relatively quickly at temperatures near 0 °C (32 °F), this protracted lifetime indicates that something is preventing the little ice crystals from recrystallizing into larger ones.
Ice hairs appear to grow from the mouths of wood rays (rather than from the bark), and their thickness is comparable to the diameter of the wood ray channels. A piece of wood that once produced hair ice may continue to do so for many years. But why is that?
When German and Swiss scientists identified the fungus Exidiopsis effusa as a major player in the production of hair ice in 2015, they finally put an end to the enigma.
This particular fungus was discovered on every hair ice sample analyzed by the researchers. There was no hair ice formation when the fungus was suppressed with fungicide or hot water.
The fungus appears to form the ice into fine hairs by an unknown process, and it is likely stabilized by supplying a re crystallization inhibitor similar to antifreeze proteins.
So, if you ever stumble across that strange white wig in the woods, don’t touch it! It’d be a minor thing if it lost all of its hair…