A couple weeks ago, I prepared about 20lbs of clay for throwing agateware. The process is to combine layers of light and dark clays in such a way that the resulting billets, when thrown, yield swirled bands of contrast in the final piece.
My light clay was Standard #240, and the dark clay was Standard #266. The #266 was firmer than the 240, so I tried moistening it before throwing. While this helped a little, I think the plasticity of the two clays are just a bit too dissimilar. I did manage to throw the clay, but there were problems with centering and opening that were clearly related to different densities in the clay.
I did end up with a couple nice large serving bowls and a tumbler and a jar and a smaller bowl. Next time around, I’ll either match two more similar clays, or make sure the moisture level is closer to even before joining them.
In any case, the results are always fun and striking.