There is a small quarry at the northwest foot of Beinn A' Chlaidh on the Isle of Berneray. I was told its clay-rich gravely soil was used for building the roads on the island - a possible source of local clay?
I sieve the earth removing all stones, then stir the remaining material in a big bucket of water. Leaving the mixture for a few minutes allows all fine sand to fall to the bottom, while the lighter clay particles are still suspended in the water. I then scoop the brown water into 2-3 layers of cotton sheets where the clay accumulates as the water slowly drains. After a day or two, a thin layer of clay can be scraped off the sheet. It is still very runny, like slip, so I leave it on a wooden board or plaster bat to dry a bit (same as when reclaiming) and finally knead it into a nice smooth lump of clay.
I do not have the knowledge to list the properties of this clay or what additions it needs to become a stable and workable clay in a traditional sense. Most ceramic artists would probably only use it as a slip for decoration or mix it into other studio clays. Nevertheless, I am exploring different sides to this clay without any addition, pure Berneray clay. So far I have discovered its beautiful bright orange colour at 1000ºC, however very fragile. At 1240ºC it melts down into a dark brown leather-like bubbly surface (see below).
Berneray clay on dark stoneware tile, fired to 1240ºC
Berneray clay tile with gathered rusty nails and other metal debris, fired to 1000ºC