There are times when this gets to be extreme. I had problems with this when after aging some slop that I had slaked down at the HS. I usually slaked the dry/leather hard clay together, and then let it sit for a few weeks to completely dissolve or soften. Then run through the pug mill. Digging through the slop I found a lot of black veins running through a clay that usually was fine. Pulled on vein out with my hands grasping it, finding that someone had pitched a piece of paper towel into the barrel. Came to realize that we had been making slab forms over rocks, cylinders, and other items using paper towel as a release liner. On finished pots no problem as it burned out. On recycled clay-too much organic material in the clay causing the smell and black veins. Is it possible you have gotten some organic material in the clay?
- D.M.Ernst likes this