A breakthrough with my problematic local clay

After countless cracks in previous batches, I successfully fired a series of mugs using clay from a nearby riverbed. I slowed down the drying process by covering them with plastic and extended the bisque firing time. The results were sturdy pieces with a unique speckled appearance. What techniques have you found effective for working with unpredictable natural clays?

3 comments

3 Comments

amy_dixon4h ago

Sometimes I wonder if we overcomplicate clay work. @hannahh22 makes valid points about grog and screening, but for casual pottery, isn't a bit of cracking part of the charm? Last year, I used unsifted beach clay for planters, and despite some fissures, they've held up for seasons. Speckles from natural impurities often add character rather than weaken the piece. Maybe rigorous testing is essential for production potters, but for hobbyists, embracing the clay's quirks can be more rewarding.

hannahh2210h ago

You know, slowing the drying process can sometimes trap moisture unevenly, which I've found creates hidden stresses in the clay body. In my experience, wedging in a bit of grog or sand does more for stability than just covering pieces with plastic. That extended bisque firing might work for your riverbed clay, but I've had batches bloat terribly from organic matter when fired too slowly. It's all about testing small scales first, because every clay source is its own puzzle. The speckled look is a nice bonus, but without screening for larger particles, you're risking weak spots. I spent a summer trying to refine local clay and learned that patience with processing beats patience in firing alone.

val5181h ago

Hannah's point about hidden stresses from slow drying rings true. I read a potter's blog that compared it to curing concrete, where rushing causes cracks but too slow can create weak layers. My own test tiles showed plastic wrap just moves the problem to a later stage.