Potters & Sculptors - Making Rock from Mud
After finishing my porcelain clay study, I have moved on to stoneware bodies. At this point, all I am doing is studying PSD (particle size distribution). Typically commercial stoneware bodies run between 10-20% large particle size ( mesh 30-70). I will not bore you with a photo gallery, but just the difference between 20% hawthorne 35m and 50% hawthorne bond 35m is very revealing. I have seen numerous clay recipes with 40-50% large clay particles in their recipe.
It is common to make up to 10% silica additions to a stoneware body pending the application. Bodies used for salt or raku often do not have silica additions because it hinders the flashing effect. However, the majority of bodies do: the silica (fines) should help to fill in the pores and fissures. I used 1200m SiC as a marker for silica in the sample below:
Let the tests continue......