|Monthly Tech-Tip |
Fired at cone 6. The samples on the bottom tiles are from ten-gram balls that have melted down (in our GBMF test). These glazes have the same chemistry, but the one of the left sources its B2O3 from Gerstley Borate (which has a high LOI). The one on the right gets it from a frit. Because the fritted version has less gases of decomposition to expel, the glass is much smoother. Curiously, the fritted version is flowing less and the red color has been lost. Why? This could be because the Al2O3, which stabilizes glazes against excessive fluidity, is being dissolved into the melt better and thus is more available for glass building.
Loss on Ignition is a number that appears on the data sheets of ceramic materials. It refers to the amount of weight the material loses as it decomposes to release water vapor and various gases during firing.
This term refers to critical thinking ability that potters and technicians can develop to recognize recipes having obvious issues and merit, simply by seeing the materials and percentages.
Gerstley Borate was a natural source of boron for ceramic glazes. It was plastic and melted clear at 1750F. Now we need to replace it. How?