I've gotten into doing clay body testing since the beginning of the year. The goal I am working towards is to create my own clay recipe. Currently, I'm working on a porcelain body formulation, and a stoneware body formulation. The cups in the foreground of the photo, below, have some iron specks in them which is coming from a clay called Hawthorn Bond. As I'm trying to attain a white stoneware body, I've switched out the Hawthorn with Tile 6 for my next round of tests. Interesting and very fun, to a potter wannabe nerd, anyways. I know lots and lots of potters who have no interest in learning about clay and glazes for their work. Not only do they have zero percent control over the clay and glazes, they are missing out on having the knowledge to take their work to another level. Potters interested in learning more should check out Matt Katz and his online courses. And no, I don't get paid to mention his classes. They are just awesome and well worth the money!
The cups in the photo are the best three clays from two different 21 point triaxial tests - the ones at the bottom are stoneware, and the cups with the handles are porcelain. The next step would be to use the three clay formulations to run a second 21 point triaxial test and that usually will yield a final formulation that can be put into production. The bars are to measure shrinkage and water absorption, the hockey puck shaped clay at the top of the photo are made to test the clay density. Knowing what your clay's specifications are tell you how good the clay will perform in your customer's home. Not knowing is not good in my experience anyways - no matter what anyone says, ignorance is not bliss!