|Monthly Tech-Tip |
These photos were taken by an iPhone 13 at 1-inch distance. They are the residue on each of the four sieves (remember I already sieved the material through 30 mesh, the top sieve thus represents the 30-40 mesh fraction). From these, it appears that the particulate in the clay is mostly rounded quartz particles. Their presence explains the sandy feel of the material during throwing (strangely, round particles generally feel sandier than angular ones). The reason it was difficult to wet-sieve through 30 mesh is that these rounded particles must be clogging the screen. It is a safe assumption that if it was tested down to 325 mesh, the percentage of quartz sand on each sieve would continue to increase. Because these particles are present at all sizes measured, the same clogging issue would occur at any mesh size. The presence of so many quartz grains also means it would be just about impossible to grind this finer than 30 mesh in a hammer mill. This being said, the presence of so many quartz particles likely means glazes will fit well (or possibly even shiver), it will have good drying performance and the plastic material should dewater quickly.
Case Study: Testing a Native Clay Using Insight-Live.com
Evaluating a clay's suitability for use in pottery
Would you like to be able to use your own found-clays in your production? Follow me as we evaluate a mystery clay sample provided by a potter who wants to do this.