Q: Why does my fired glaze leave exposed clay areas?
Some defects have one or two possible causes that result in a fast correction. However, other types of defects have many possible causes. It is often best to start with the elimination of factors and concentrate on the remaining causes. This article is long but hopefully contains information that will be of use in the future. At some point you will experience one or more of the defects covered below.
• If the dry (unfired) glaze on the pot is dusty or fragile when handled it might crawl in the glaze firing.
• If a fired glaze looks like beads of water on a glass table top, you're looking at crawling.
The same forces of surface tension acting on beading water can also affect fluid molten glaze. Glaze crawling can have many possible causes; in some cases a few solutions can be tried simultaneously to fix this common problem. First, make sure the problem is crawling and not a similar defect. The glaze should appear beaded up or have rounded edges where it draws away from the exposed clay body. The bare patch of clay body can be quite dry or have a slight shine to its surface. In extreme cases of crawling, beads of glaze have dropped off the pot and can be found on the kiln shelf. If the glaze has the potential to crawl, thicker glaze applications will exacerbate this defect. If any of these glaze characteristics are noted, crawling is present.
Crawling occurs when the unfired glaze and the underlying clay body do not build and hold a uniform continuous bond. The most common causes of crawling are listed in their
