The outer bark of the birch is called näver. It has been used all throughout history; 5000 years old birch bark boxes were found with the Iceman mummy in the Italian Alps in 1991.
The bark is waterproof and highly resistant to rot and decay and was used to waterproof turf- and grass roofs. A birch bark roof stayed waterproof for 50 – 60 years.
In the 16th century birch bark could be used to pay taxes.
North American natives built t their famous canoes from birch bark and it was common practice to use it both for floats and wrapped around stones as sinkers on fishing nets.
Birch bark is resilient, strong and easy to shape. Bark from downy birch is preferred, being smoother and whiter than bark from silver birch. Bark is harvested earl y in summer when the sap is high. If the outer bark is carefully removed, the inner bark protects the tree and a new layer of outer bark will form. You need permission from the land owner to harvest bark.
Bark can be harvested in sheets or in narrow strips by cutting it in a spiral. Sheets can be used for boxes, back packs or sewn containers, the strips for various basket weaving projects.