I tried pouring a large plain stein today. I let is set long enough, but when i tried to seperate it the bottom ripped and showed to be very thin and stuck to the mold. there must have been some water a long time ago that developed into mold on the inside surface. this actually  clogged the pores of the mold not letting the moisture of the slip to be pulled in which caused the walls to form. it also did not allow the ceramic piece to cleanly seperate. so now we have to find a way to get rid of the mold for it to be usable.