This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. T. Neil Davis is a seismologist with the Institute. The making of stoneware pottery seems to be a growing activity in the north, perhaps as many as a hundred Alaskans are spending considerable time at it. Some use imported clay, but many dig their own at Healy, Alaska, or other localities.
Plasticity is the essential feature of clay that makes pottery production possible.
It derives from the plate-like shape of clay particles, very thin but elongated in two dimensions. This shape gives extensive surface area for adsorbing of thin layers of water molecules which bond together the clay particles but allow them to slip past each other when clay is thrown on a potter's wheel or otherwise fabricated into particular shapes. Very tiny, of the order of one-thousandth of a millimeter in length, clay particles result from weathering, grinding up and disintegration of rock materials. The secondary clays usually have greater plasticity than the primary clays. The clay layers intermixed with the Healy coal beds are highly plastic secondary clays.