When glaze crawls
Three bowls from the July firing came out with bald patches where the glaze had pulled back from the clay and rolled up into thick beads at the edges. Crawling. It is one of those faults that looks dramatic and usually has a boring cause.
In my case there were two. The bisque ware had sat on an open shelf for a fortnight collecting dust, and I had applied the glaze far too thickly in a single long dip. Dust stops the glaze gripping, and a thick raw glaze layer shrinks as it dries and cracks before it ever reaches the kiln.
The fix
- Wipe bisque with a barely damp sponge before glazing.
- Dip for a count of three, not five.
- If the dry glaze shows hairline cracks, wash it off and start again. Hoping is not a technique.
One of the crawled bowls has a beautiful pattern of beads across the inside, so it stays as a fruit bowl. The other two went back to the beginning.