|Monthly Tech-Tip |
This body is used in the sanitary ware industry in China, the supplier sends this report with each shipment. The chemistry and assorted values for porosity, shrinkage, particle size are provided. The factory receiving this report accepts it as gospel and goes into production. However engineers at the plant need to think twice about such reports. These tests are being done at one temperature, they say nothing about what that body is doing above and below that temperature. Is it being employed in a volatile range of the porosity or firing shrinkage curves? Zero porosity bodies of this type are best when fired to a point near where the porosity curve descends to reach the x-axis. However that curve remains at zero while the shrinkage one tops out and reverses direction. At some point the porosity curve sharply rises. Only by firing and testing at a range of temperatures in your own lab can you where your body is on the curve.
In ceramics, glazes and bodies have a chemistry, a mineralogy and a physical presence. All of these need to be understood to adjust and fix issues.