|Monthly Tech-Tip |
The cone 6 porcelain on the left uses Grolleg kaolin, the right uses Tile #6 kaolin. The Grolleg body needs 5-10% less feldspar to vitrify it to zero porosity. It thus contains more kaolin, yet it fires significantly whiter. Theoretically this seems simple. Tile #6 contains alot more iron than Grolleg. Wrong! According to the data sheets, Grolleg has the more iron of the two. Why does it always fire whiter? I actually do not know. But the point is, do not rely totally on numbers on data sheets, do the testing yourself.
Standard porcelains used by potters and for the production of sanitary and table ware have surprisingly similar recipes. But their plasticities vary widely.
Ceramic materials are employed in the ceramic industry to make glazes, bodies, engobes and refractories. We study them at the mineral, chemical and physical levels.
In ceramics, glazes and bodies have a chemistry, a mineralogy and a physical presence. All of these need to be understood to adjust and fix issues.