Hair Ice: Even Cooler Than You Thought

Story and photos by Kim Brown

You’ve probably seen hair ice while hiking on a cold day. You might have thought it was a weird fungus. You may have even asked on a mycology forum or a trip report, “What kind of fungus is this?” If, however, you ever lean down to examine it and give it a touch, you’ll discover that it melts away from the warmth of your hand.

“Hair ice” is a beautiful winter wonder. While not rare, it can be difficult to find because it is formed under a variety of particular conditions. Hair ice is formed at a particular temperature between latitudes of 45 and 55 degrees, during a particular time of day and on a particular type of wood, which must be free of bark. It also requires the presence of a particular fungus — and, of course, you have to be there to see it before it melts!

Simply speaking, hair ice is formed when moisture fizzes from a bit of wood and instantly freezes, creating delicate, angel-hair-like strands in mid-air.

Big surprise: There’s more to it. A nuclear action within a freezing layer of water pushes liquid water through pores of the wood and into the freezing air. But beyond that, a particular fungus has a role in the formation of the hair ice structure.

A study published in the journal Biogeosciences, in 2015, found that the fungus Exidiopsis effusa was found in all samples of hair ice in the study samples. Without E. effusa, ice will still form; however, it would be in a more stable shape, like a crust or blob, not the fragile shape of hair ice. The presence of the molecules lignin and tannin within the wood also play a role in the shape of hair ice.

Thanks to better technology, we are discovering more and more about our natural world. While hair ice is not a new discovery, nor is the thought new that a fungus plays a role in its formation, recent science has confirmed that hypothesis. Because this confirmation is so new, studies are still being conducted to understand the exact roles that E. effusa plays in the formation of hair ice.

You will have the best luck finding hair ice on mornings that are sunny after a night of temperatures cold enough to form ice. The Lime Kiln Trail near Granite Falls and Federation Forest State Park (near Enumclaw) are trails where hair ice can reliably be seen, but anywhere barkless hardwood like alder can be found on the ground is a good place to look.