... To start fires, the Vikings would use a type of fungus called Fomes fomentariuswhich is found in Europe, North America, and Asia.

It is better known by the names Tinder Fungus, Hoof Fungus, Touchwood, or False Tinder Fungus.

Now, a lot of fungi make great tinder for starting fires with sparks. But the Vikings didn’t just carry around the Tinder Fungus. They transformed it into something even more ignitable.

First the Vikings would prepare the Tinder Fungus by cutting away the exterior pieces. The interior pieces were cut into thin slices.

The fungus slices were beaten until they started to become soft, flexible, and resemble felt.

The fungi “felt” was charred in the same way that char cloth is made – by burning it in an oxygen-less container. Making char cloth isn’t anything new to survivalists. But the Vikings took it a step further.

They boiled their fungus char cloth in urine!

Urine contains sodium nitrate, which has very similar chemical properties as potassium nitrate (the “saltpeter” found in gunpowder”). ...