Q&A: Diagnosing Glaze Blisters

A glaze blister is one of the most vexing defects, and it is one of the most complicated to diagnose as there are so many possible causes. Often the potter thinks they are correcting the fault only to discover it continues to surface in subsequent firings. Glaze blisters appear as pronounced sharp edged burst bubbles that look like craters on the fired glaze surface, often revealing the underlying clay body. Glaze blistering can really tax potters' investigative abilities. Any exploration into this common defect will require an analysis of kiln firing, clay body, and glaze conditions. The priority is to accurately diagnose the problem, then determine what incident or series of events caused it. Only then will it be possible to enact the appropriate correction.