Originally Posted by The Forge
The mold is a sign on the clay aging, which is a good thing. Chinese potters used to bury a large amount of clay in a pit to 'age'. This 'cache' was to be used by their sons. When I was grad. assistant I worked with a ceramicist in the sculpture dep't. We used to make the clay to a recipe that he had. The best batches for 'throwing' were mixed before a vacation and left to 'age' during the time off. The 'aging' develops a mucilage between the clay particles.
thanks for the information