From May 1 to May 10, 2009, the science festival “basecamp09 festival science et cité” took place in Zurich. The Unit Soil Science and Biogeography offered a workshop where children could create pictures using colours made from soil. This workshop had been designed and was supervised by Anett Hofmann, Jolanda Kasser und Michael Schmidt.
About 80 to 100 children between 4 and 12 years of age attended the workshop "Diversity of colours in soil". The children used both paints made from fine soil particles (clay and silt) and coloured sand to create their own pictures which they could take home afterwards. Some didactic tricks were used to explain the origin of the different colours in soil: The children could use a magnet to fish iron particles from a reddish-brown Jurassic soil, or compare soil colour to that of a rusted horseshoe. Reddish and yellow colours in the soil originate from the presence of iron oxides (rust). Thus, it was very easy to understand for both children and parents that iron makes soils colourful. Therefore, the soil colour workshop not only had an aesthetic appeal, but also conveyed basic soil science knowledge.