I have been studying plasticity in stoneware bodies, as most know. I am finding some results that are making me question the accepted belief that plasticity equates to ease of throwing. Plasticity in general comes from the electrostatic charges on the clay particles; which changes as the body ages. I am looking for articles that specifically review the relation of sub micron ball clays, to the ease of throwing. I am trying to determine/figure out how mass plays a role in throwing.
Ron Roy and I had this discussion at NCECA; what is the cut-off point for large and intermediate mesh sizes, before those additions create a denser mass: which makes the clay harder to push around on a wheel. It is very common for stoneware bodies to have 80% total clay content, there are some even higher than that. So I still find myself questioning if mass is playing the larger role in determining if a clay is easier to push around? Not sure if I am articulating my thoughts correctly, but hopefully I have made the question clear enough.
As a comparison: everyone knows how easily porcelain moves around when thrown. The most common analogy is that it throws like cream cheese. That is because porcelain in general has 25% silica, and 25% feldspar; which has much less mass than fire clay. One of the major differences is mass: stoneware has more clay content; and much larger particle sizes. I have tested this theory by adding V-gum and macaloid to high percentage formulas of fire clay/intermediate clay. These additions are not the norm; solely done to test if plasticity is the determining factor in ease of throwing.