The rather extreme (for here!) weather these past few days has shown me a couple things that have made me go ‘Wow!’
Putting aside the strange phenomenon of full-on sunshine in Central Brittany for six consecutive days. The first, admittedly banal, occurrence was that the sheets I put on the line to dry froze like cardboard in the icy wind!
However, much more interesting was finding hair ice in Beffou Forest on Friday. I did not know what this was, nor that it even existed, and now after some research, and finding that it is quite rare, I wonder if I’ll ever see it again?
From typing ‘ice crystals wet wood’ into the machine this is what I found….
Hair ice (also known as ice wool or frost beard) is a type of ice that forms on dead wood and takes the shape of fine, silky hair. It is somewhat uncommon, and has been reported mostly at latitudes between 45–55 °N in broadleaf forests. The meteorologist and discoverer of continental drift, Alfred Wegener, described hair ice on wet dead wood in 1918,[assuming some specific fungi as the catalyst, a theory mostly confirmed by Gerhart Wagner and Christian Mätzler in 2005.]
Hair ice forms on moist, rotting wood from broadleaf trees when temperatures are slightly under 0 °C (32 °F) and the air is humid. Each of the smooth, silky hairs has a diameter of about 0.02 mm (0.00079 in) and a length of up to 20 cm (7.9 in). The hairs are brittle, but take the shape of curls and waves. They can maintain their shape for hours and sometimes days. This long lifetime indicates that something is preventing the small ice crystals from recrystallizing into larger ones, since recrystallization normally occurs very quickly at temperatures near 0 °C (32 °F).
The hairs appear to root at the mouth of wood rays (never on the bark), and their thickness is similar to the diameter of the wood ray channels. A piece of wood that produces hair ice once may continue to produce it over several years.
In 2015, German and Swiss scientists identified the fungus Exidiopsis effusa as key to the formation of hair ice. The fungus was found on every hair ice sample examined by the researchers, and disabling the fungus with fungicide or hot water prevented hair ice formation. The fungus shapes the ice into fine hairs through an uncertain mechanism and likely stabilizes it by providing a recrystallization inhibitor similar to antifreeze proteins. (Thanks Wiki).
And here’s what it looks like!
It melts, as you would expect, the minute you touch it. That it stayed in such good condition even in the sunshine, until I got back to the car to photograph it shows how cold the day was!