In this episode of For Flux Sake, I dig into what people call “carbon coring” in clay bodies—those dark/black cores you sometimes see in a broken cross-section after firing. The big takeaway: the name is kind of a misnomer. Yes, carbon and burnout matter, but the thing that really makes that dark core show up is iron chemistry—especially in reduction-fired bodies where iron is common and the atmosphere can push iron into reduced states that read as gray/black. I talk through what’s happening inside the clay during heatwork: gases trying to escape, oxygen availability in the body, and how firing schedule and clay thickness can stack the deck toward incomplete burnout and reduced iron in the interior. We also get into the practical question—should you care? Sometimes it’s mostly cosmetic, and sometimes it’s a signal that your firing (or your clay choice) is setting you up for strength, maturity, or defect issues. We round out the episode with listener questions on kiln safety and studio best practices—especially the stuff that matters when kids and pets are around—because “materials science” isn’t just recipes, it’s how you run a studio without getting hurt.