Tinder fungus, Fomes fomentarius, is a cryptogam growing on dead birches. Before the invention of matches it was used as tinder in making fire. It is grey and hard before being prepared.
Slices of the central, brown part is boiled or soaked in a mix of water and birch ashes or nitre. When dried and pounded soft and thin with a wooden mallet, they resemble chamois leather.
Tinder is highly inflammable and is used to catch a spark caused by striking metal and flint together.
Tinder, not soaked in nitre, has been used for making clothes. Livrustkammaren in Stockholm have a hat and a coat made from tinder fungus, dating from early in the 18th century. Up to about 1920 clothes were made from tinder in central Europe.