|Monthly Tech-Tip |
Rutile blue glazes are difficult, blistering and pinholing are very common. You must get it right on the first firing because pinholes and blisters will likely invade on the second. On the second firing the melt fluidity increases, the glaze runs and creates thicker sections in which the bubbles percolate and just do not heal well during cooling (even if it is slow). When finishing leather hard or dried ware do not disturb thrown surfaces any more than necessary. Make sure that ware is dry before the glaze firing. Do not put the glaze on too thick. Limit the melt fluidity (so it does not pool too thickly in any section). Do not fire too high. Drop and hold firing schedules can help a lot (coupled with a slow cool if needed).
Questions and suggestions to help you reason out the real cause of ceramic glaze blistering and bubbling problems and work out a solution
Refiring pottery and porcelain comes with many issues that can ruin ware, knowing about these will help you do it successfully.
Rutile Blue Glazes
A type of ceramic glaze in which the surface variegates and crystallizes on cooling in the presence of titanium and iron (usually sourced by rutile)