We all like to be our own Chemist. We take pride in ordering raw materials and weighing out each powder, mixing and applying, and we glory in the joy of the results. It's magic.
But do you ask enough questions of your raw materials? When you order feldspar or Spodumene is the name all you need to know about it. Try asking your pottery supply house for a certificate of analysis for these raw materials you are buying. This is not easy to get. You should get some verification as to the chemistry AND the particle size distribution. The chart in the picture here is from one of my favorite texts (The Chemistry And Physics of Clay by Grimshaw) and shows how three very different distributions can all be labeled as 36 mesh. The behavior of these three different powders can be very different in your clay body or glaze. It will have an impact on plasticity and on the amount of liquid required for your application. So.... Start asking, paying attention and thinking about it.
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