Clay is a vital part of earthen plasters, earthen floors and cob.
Ideally we want to harvest our clay from the local area, but how do we know how pure the clay is?
Jacob Deva Racusin from New Frameworks Natural building shows us his testing method.
A rough gauge I personally use:
After thoroughly mixing some site soil with water and working it until there are no lumps
If you can roll the site soil into a ball there is at least 10% clay present.
If you can roll that ball into a sausage shape, there is at least 20% clay present.
If you can then bend that sausage around into a donut shape, there is at least 30% clay present.