Suitable for use in all clays (throwing too), 35 mesh kyanite is a medium coarse grog added to clay bodies primarily to reduce dry shrinkage stress that leads to cracking. In clays fired above 1100º C, it fires off-white and begins to expand as it converts to mullite, effectively reducing the clay’s fired shrinkage.
With a little clay and sodium silicate, excellent refractory mortars can be made with kyanite.
For more information on kyanite, see the Digitalfire.com Reference Library of ceramic materials.