grind coal extender
Grind punky wood and certain fungi to make coal extenders for your fire. Tim MacWelch

Fire almost always begins with tinder. I often explain it to my classes like this:

Tinder is the “baby food” for your baby fire. But if a wad of fibrous tinder is like a jar of Gerber carrot mush, then what’s equivalent to mother’s milk? In my mind, coal extender is the finest grade of tinder, and the first food for traditionally started fires.

Coal extender is virtually any material that is fine textured and flammable enough to add directly to a coal or ember in order to make it larger and keep it going longer. Coal extender can be added to a coal while it’s still in the notch when you’ve made a bow drill ember. Or it can be added to the core of a tinder bundle when you’re using flint and steel or a magnifying glass to kindle a blaze. You can add it to an existing ember, or place it where an ember will go. Many good coal extenders are already a fine fiber, and the rest should be easily turned into dust, fiber, or powder. You can grind coal extender material between two rough stones as if you were milling flour. Scraping can also work, and it can be done with a sharp stone or metal blade. Filing or sawing can make a great powder. Some coal extenders can even be crumbled into dust bare handed. And all coal extenders should be as dry as possible when being used.

Here are just a few of the coal extenders that I like to use in my friction fire, flint and steel, and optical fire making kits.

Dust From Friction Fire Attempts (that didn’t ignite)

That’s right. If your dust didn’t light from a bow drill or other friction fire attempt – save it! Add that dust to a coal that did ignite and it will get bigger!

Fine Bark Fibers

Cedar bark powder is one of my favorites, as it tends to smolder for a long time. However, any bark that makes suitable tinder should make fibrous dust for coal extender. I often pound my bark tinder with a rock to fluff it up, and this process naturally creates fine dust. Scoop it up and use it for your extender.

Polypore Shelf Fungi

Cracked cap polypore is one of favorite shelf fungi for coal extender. This odd and rock-hard shelf fungus grows on dead or sickly black locust trees, and its brown woody core can ground into good coal extender powder. Incidentally, you can also start an ember burning on a chunk of this fungus and carry the live ember for hours (on large specimens).

Punky Wood

If a rotten piece of wood can be crumbled into fine dust with your bare hands then it’s a candidate for coal extender. Punk (as this decayed wood is sometimes called) can be ground into a coarse powder and added to any coal. Weed Tops and Seed Down Cattail down, milkweed down, goldenrod tops, even dandelion fluff—these can all act as coal extenders, and they require no processing other than tearing them off the plant.


Inonotus obliquus, also known as chaga mushroom, is a parasitic fungus found on birch and oak trees (among others). The crusty conk is an irregularly shaped mass with a burnt-looking exterior and a velvety caramel colored woody interior. This can be ground into powder with an extremely low ignition temperature. It’s possible to strike flint & steel sparks into raw powdered chaga, and they will ignite as if the powder were excellent char cloth.

Have you used coal extenders for traditional fire starting? Please let us know by leaving a comment.