An example of how calcium carbonate can cause blistering as it decomposes during firing. This is a cone 6 Ferro Frit 3249 based transparent (G2867) with 15% CaO added (there is no blistering without the CaO). Calcium carbonate has a very high loss on ignition (LOI) and for this glaze, the gases of its decomposition are coming out at the wrong time. While there likely exists a firing schedule that takes this into account and could mature it to a perfect surface, the glaze is high in MgO, it has a high surface tension. That is likely enabling bubbles to form and hold better.
Troubles |
Glaze Blisters
Questions and suggestions to help you reason out the real cause of ceramic glaze blistering and bubbling problems and work out a solution |
---|---|
Glossary |
Decomposition
In ceramic manufacture, knowing about the how and when materials decompose during firing is important in production troubleshooting and optimization |
Glossary |
Surface Tension
In ceramics, glazes melt to produce a liquid glass. That glass exhibits surface tension and it is important to understand the consequences of that. |
Glossary |
Blisters
Blistering is a common surface defect that occurs with ceramic glazes. The problem emerges from the kiln and can occur erratically in production. And be difficult to solve. |
Materials | Calcium Carbonate |
Articles |
Firing: What Happens to Ceramic Ware in a Firing Kiln
Understanding more about changes are taking place in the ware at each stage of a firing and you can tune the curve and atmosphere to produce better ware |