|Monthly Tech-Tip |
They will delaminate somewhat during bisque, Handle joins will crack somewhat during drying. They are splitting at the rim during throwing. The glazes will craze on all of them. But the extent and manner in which these things happen will enable me to compare them. These are kaolins (mixed with feldspar) to vitrify around cone 6. I am comparing current shipments with previous ones. This demonstrates the value of a potters wheel in directly judging absolute and comparative plasticities and drying properties and providing specimens to testing glaze fit and coverage.
The purest of all clays in nature. Kaolins are used in porcelains and stonewares to impart whiteness, in glazes to supply Al2O3 and to suspend slurries.
A fine particled highly plastic secondary clay used mainly to impart plasticity to clay and porcelain bodies and to suspend glaze, slips and engobe slurries.
A clay deposit that is near the site of erosion and alteration. They have more mechanical impurities and fewer chemical and mineralogical impurities. Primary clays have larger particles and less plasticity.
Ball clay is the most common type of secondary clay. They are much more plastic than kaolin because