Fomes fomentarius, the “Tinder Fungus” (by )

Mushroom of the Month: October, 2014

Recently four small specimens of Fomes fomentarius were gifted to me by a friend returning from the FFSC Alaska foray.  I was delighted, but not for the usual reasons.

Most of us enjoy the process of walking through moist forests in search of fungi for the table.  For some of us, it is the hope of finding a rare or unusual species that draws us to the woods.  But in a time before matches and Bic lighters, a hike in the woods yielded fungi that held the promise of a fire.

In Europe, back in the day when flint and steel started your fire, “German tinder” was sold.  It was an industry of sorts involving the collection of Fomes fomentarius, a birch-loving conk.  From this fungus, a light brown felt was produced with the feel and look of soft buckskin.  This fungal felt is commonly known as “amadou”.  This processed polypore felt had many uses.  It could be fashioned into clothing like hats and vests when  leather was scarce.  But for German tinder, it was saturated with salt peter (potassium nitrate).  This is the same stuff that gives gunpowder much of its explosive force.

The folks who made the tinder didn’t necessarily know the chemistry, but they sure knew how to make tinder “quick”, quick to catch fire that is. The source for this salt came from soiled straw from stables heaps.  Piled in rows, the urea in this stable waste underwent bacterial decomposition to form first calcium nitrite, then eventually calcium nitrate.  Water was poured through the heap, collected, then filtered through white wood ash (containing potassium carbonate).  The calcium nitrate salt converts to potassium nitrate as it reacts with the potassium carbonate.  This nitrate rich solution was then decanted, sopped up with the amadou, then dried. Natural sources of potassium nitrate crystals can sometimes be collected directly from bat cave walls and old stables.  (A note of caution here.  If you try this at home, and you get a little too much saltpeter in your amadou, be prepared for an explosion rather than “quick” tinder.  Burn injury is a real risk.)

Fomes fomentarius amadou tinder.  Photo by S Labiste

But Germany’s tinder manufacturers were not the first to discover the relationship between Fomes fomentarius and fire. Long before nitrate-enhanced amadou was in use, before Europe even had cities, this fungus was in use as a tinder. In 1991 a late Neolithic man melted out of a glacier in the Ötztal region of the Italian Alps.  Ötzi, as he came to be named, carried tinder fungus Fomes fomentarius).  He may also have carried it for its medicinal qualities, but his knife shows traces of marcasite, so he apparently used the knife as a striker in his pyrite/flint fire kit.  The last time he used the kit was 5,400 years ago.  Most likely he needed the Fomes fomentarius he carried to kindle a fire in that alpine winter environment.  Even without creating a fungal felt, the trauma layer of this conk can be scraped into a fluffy mass then ignited with a small spark.  The term “amadou” can mean either the felt or the fluff from this fungus.

To appreciate amadou one has to realize how difficult it can be to obtain really good tinder material in the wild.  I’m talking about tinder that will catch a spark from flint and steel or flint and pyrite/marcasite without first being charred.  Most flint and steel enthusiasts use charred punk wood, charred cotton cloth, or charred plant pith.  Unless you carry some form of charcloth in the field with you, you have to first make a fire to make the charcloth.  If you are relying on flint and steel or flint and pyrite for that fire, you are in a bit of a fix without charcloth.  So it’s useful to know about tinders that work without charring.  Mors Kochansky, survival guru of the boreal forest, teaches the processing and use of this tinder material.  Amadou isn’t the only good tinder, but it sure is an appealing one.

You will see Fomes fomentarius referred to as both tinder fungus and false tinder fungus.  It is also known as horse hoof fungus, tinder polypore, tinder conk and touchwood fungus among others.  Even more confusing, the term “false tinder fungus” is applied to both Fomes fomentarius and to a similar birch-loving conk, Phellinus igniarius.  Common names can be confusing since they vary depending on the region.  The terms tinder fungus and true tinder fungus are also used to describe an entirely different fungus, Inonotus obliquus (chaga).  Chaga is an incredible tinder which can be used without processing, or it can be powdered, but it does not produce a felt.  Like Fomes fomentarius, it is found on birch (though not exclusively birch) and is rare in our area.

Amadou felt had other uses.  It has an amazing ability to absorb moisture.  Dentists once used it to dry teeth before a blast of air came into vogue.  Podiatrists used it to pack the sides of toenails prone to inflammation.  It has been used to staunch bleeding and to serve as a wound dressing.  To this day fly fishermen use it to dry fishing flies and it can be purchased on line.  It has medicinal qualities, was used as a razor strop, and it is even used to make “smoking hats”… wait, a flammable hat for smoking?  What were those Germans and Hungarians thinking?

Then too, the tube layer has its use in relation to fire.  A small section of the tubes, set to rest in a pool of fat or oil becomes a wick for a candle.  It draws the liquid to the flame and remains unconsumed until the oil is completely burned.  It, and the tubes of other polypores, appear to have been used as wicks in the fat lamps of Cro-Magnon man.  

No wonder it flaunts its relationship to fire in its name. The Latin word fōmĕs means touchwood or tinder.