Frost Beards

Has there been a wild shaving party in the Ennerdale woods? Will we be finding out what Santa looks like without a beard? Or is Jack Frost playing a whiskery joke? 

In fact it is something more fantastical than any of these - the rarely seen and only lately understood phenomena, ‘Hair Ice’ or ‘Frost beard’.

It is rare because it is extruded from rotting wood only when specific conditions apply. It only occurs in deciduous forest; only between 45 N and 55 N latitude; only on humid nights; only when the temperature hovers at about 0 C; only when frost is forming and crucially; only when fallen branches 3 to 8 cm in diameter have already been invaded by one particular fungus, Exidiopsis effusa.

The fallen branches were laid at random under a stand of bare beech trees, each one partially covered by pure white fronds of hair, lying as if neatly combed before being stuck on.  Strangely, these venerable beards still persisted, despite there being no other signs of frost just there and the temperature mild in the mid-afternoon.

Wise and probably hairy men of the past have examined them and for a time it was thought a gas from the rotting wood pushed the hairs of ice out. This was a load of hot air though. Alfred Wegener (also discoverer of continental drift ) postulated that a fungus might be involved but it was only in 2015 that a scientific investigation revealed that it is a complex process, beginning with ice-segregation. In this case where the formation of ice creates a suction over the rotting wood’s medullary rays, pulling out water from these pores into fine hairs. Within the freezing liquid are traces of lignins and tannins, from or as a by-product of the fungi, which prevents re-crystallisation into more solid clumps. There is also some kind of ‘stay-frozen’ chemical which inhibits the structure from melting if temperature warms slightly.

Amazing and entrancing, with the added bonus that, ‘If you go down in the woods today it’s easy to find a disguise!’