|Monthly Tech-Tip |
If you are trying to use local clays for brick or tile or even pottery production, characterizing the available materials is the first step. But how? This is the kind of data a lab might submit and perhaps you wonder about its value? We feel traditional ceramics technology is fundamentally relative. A history of many reports like these, in context with other data, might be good for mining companies to determine if new stockpiles have any shifts in certain specific properties. But as a way to understand the utility of a clay for a specific purpose, this contextless report is of little use. It is also a tunnel vision view, looking at only one temperature. On the other hand, simple procedures like the SHAB test provide a hands-on way to understand what a clay actually is.
Factory technicians often just see clay materials or bodies as data sheets full of numbers. Similarly, knowing the statistics of a pro sport can make one feel like an expert. But there is no substitute for actually playing! Likewise, taking the time to actually slurry up a clay body and hand-make and fire ware using it is the way to really notice it’s characteristics. I make coffee mugs, doing it the same way each time. Notice what these mugs tell me. The rims have pulled oval, the color is dark and solid and the foot is plucking: The body is too vitreous. Sandy particles can be felt on the rims (also felt during trimming and throwing). When pulling the handles splits formed, indicating low plasticity (this was also evident during throwing, I was unable to pull the walls as thin as normal). Dry strength is low, the lower handle-join dry-cracked on the convex side. The inside glaze is also revealing that iron speckle is excessive.
In ceramics, this normally refers to the process of doing physical or chemical testing on a raw material to accurately describe it in terms of similar ones.
Brick-making is surprisingly demanding. Materials blending and processing, forming, drying and firing heavy and thick objects as fast as possible are like no other ceramic manufacturing challenge.