I decided that the process and the material had to be environmentally responsible. Cob is an earthen building system that uses a mixture of clay, sand and straw. It is environmentally friendly and also culturally appropriate, since it was commonly used through much of pre-war Europe. There is a renaissance of interest in Cob as people re-discover 'greener" building technologies. Given a foundation and a roof, Cob is a permanent material. However, since these structures are unroofed, they will melt away into the forest. In this way the artworks have a life cycle, reflecting the Waldkunst 2008 theme of Cycles and Systems.