Ryan M Miller

A lot of entry level gardening books on soil health define clay particles solely by size (2 μm and smaller). This is generally fine for defining soil texture, but not useful for defining a pottery clay body since not all particles in this size range have the properties of clay minerals. In addition to regular illite, bentonites, montmorillonites, kaolin, and other aluminum silicates, there may be other particles in this size range that do not add clay plasticity or expansiveness; for example, if I have a bag of pure quartz particles (silicon dioxide) that are 2 micrometers and smaller and then I attempt to add distilled water to it to make a clay body, would the resulting paste still have any plasticity or wet strength to it that would make it useable as a clay body? I feel that I would be lucky if I at least get some kind of melted glass that leaves a mess in a kiln from such a "clay" body. What if I have a bag of dried peat or muck particles that are 2 micrometers or smaller? The resulting paste when water is added would not be suitable for firing in a kiln even if it does have suitable plasticity or wet strength since it would just burn away if it were fired in an oxidizing environment. Similarly, if I attempt to make a clay body of limestone (mostly calcium carbonate) that has been ground down to 2 micrometers or smaller, the resulting paste would just reduce in the kiln, turn into caustic quick lime, and gradually crumble apart as the fired object is explosed to atmospheric moisture.