An example of how a carbonate can cause blistering. Carbonates produce gases during decomposition. This glaze (G2415B) contains 10% lithium carbonate, which likely pushes the initial melting temperature down toward the most active decomposition temperatures.
Questions and suggestions to help you reason out the real cause of ceramic glaze blistering and bubbling problems and work out a solution
In ceramic manufacture, knowing about the how and when materials decompose during firing is important in production troubleshooting and optimization
In ceramics, glazes melt to produce a liquid glass. That glass exhibits surface tension and it is important to understand the consequences of that.