Creepy Crawler

Here's a glaze worth pursuing.  Or rather perfecting. I love the purple color, the satin finish, the way it breaks over edges. What I don't like is the uneven thickness and its tendency to crawl leaving bare clay spots. 

Now this is the project for the next round of firings. Soooo....... What are the causes of these defects?

Let's start with the crawling defect. This can happen in the raw glaze because of drying cracks, dust on the surface, or a drop of oil or wax resist. It can also happen during the early  stages of firing as the carbonates burn out. Zinc oxide, wollastonite or bone ash can contract excessively at high temperature.  High viscosity and surface tension in the melt can also contribute to crawling. 

For the unevenness, the flow behavior of the raw glaze mix has the biggest impact on a uniform application. But again, the high temperature viscosity of the melt will also either help or hinder leveling. 

So.... Stay tuned...  The creepy crawler will be banished at the next glaze session.