Sub-soils used for the making of cob in Cornwall must contain several different elements to ensure a successful pre-manufacture, manufacture and cure. The graph above displays a typical combination of natural materials that is proven to be effective throughout these processes and is one of many reasons why Earth Blocks Ltd are carrying earthen and cob architecture out of the darkness of misconception in the UK. Data collection for volumes of individual elements provides the designer and/or user with crucial information when specific intelligence is required to establish product content and assists the self-builder with appropriate soil identification when excavating potential source sites.
Cob block and cob brick weights are determined by their individual material components at source and, more importantly their moisture content during pre-manufacture, manufacture and once cured. On average, our cob products will lose 13% of their manufacturing weight when dry and almost 50% of their weight from initial mixing to shelf. To throw a curve-ball into these findings, some aggregates/gravels, particularly in Cornwall, are naturally heavier. For example, in some areas of the South West Hematite stone courses through the veins of the clay (generally red in colour) and this can be up to 30% heavier than that of the common sedimentary rock. Once again though, individual [component] weights are reasonably adjustable and need not be ‘to the gram’ to be successful.