Foundry Hill Creme (FHC) is used in North America as a stoneware body base or addition. It fires like a ball clay, but it is less plastic. How much feldspar would it take to make it vitrify to zero water absorption? I code-numbered pure FHC as L3146B and fired SHAB test bars from cone 4 to 10 and 10R (note the soluble salts). The firing shrinkage and water absorption data calculate in the red columns (and plot on the blue lines). Notice the steady drop in absorption and rise in firing shrinkage, from cone 3 to 10 (and 10R). An 80% FHC and 20% nepheline syenite mix plots to the orange lines. Notice cone 9: The absorption hits zero while the firing shrinkage is a steady 1.5-2% more than pure FHC. The drying shrinkage of the two can also be compared. It takes a 35% nepheline addition to most ball clays I have tested to achieve near-zero absorption; it appears this is going to need the same. This kind of data is what enables recipes to be created.

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Suddenly, ware is coming out of your production kiln warped or cracked or off color. Unless the answer is obvious, the first action should be to compare its drying and firing test data with past runs. If you are doing that as a routine, then SHAB test bars (and the test result data they bring) will already be available. These bars are tests of slip casting bodies, they can be made in a plaster mold and length-marked as shown. That data is a characterization of the clay body. The value of this kind of data-gathering becomes evident when a disaster happens (or better yet, is prevented). Clay bodies have plasticity, dry performance, dry strength, fired density, fired shrinkage, fired strength, etc. If you have historical data (accompanied by firing schedules, recipes, etc), you have an invaluable tool. Where does one gather the data? In spreadsheets? No, in a database. An account at Insight-live.com is specifically intended for this.
| Materials |
Foundry Hill Creme
FHC is used in North America as a stoneware body base or addition. It fires like a ball clay, but it is less plastic. |
| Articles |
Setting up a Clay Testing Program in Your Company or Studio
Set up a routine testing pipeline and start generating historical data that will enable your staff to understand your source materials and maintain, adjust and troubleshoot your clay body recipes. |
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