Electron micrograph showing Dragonite Halloysite needle structure. For use in making porcelains, Halloysite has physical properties similar to a kaolin. However it tends to be less plastic, so bodies employing it need more bentonite or other plasticizer added. Compared to a typical kaolin it also has a higher fired shrinkage due to the nature of the way its particles densify during firing. However, Dragonite and New Zealand Halloysites have proven to be the whitest firing materials available, they make excellent porcelains.
|Materials||New Zealand Halloysite|
Clays used in ceramics shrink when they dry because of particle packing that occurs as inter-particle water evaporates. Excessive or uneven shrinkage causes cracks.
What is clay? How is it different that regular dirt? For ceramics, the answer lies on the microscopic level with the particle shape, size and how the surfaces interact with water.