Amy McClure makes these impecable pieces in her Boston MA studio exclusively for Oakleaf & Acorn. All Oloria studio goods are made from stoneware clay or stoneware porcelain and fired to a vitreous cone 6 (2200degrees F). This means they rae typically very strong and Durable when cared for properly. All All high fire porcelain and clay incurs some slight warping during the firing process. Pieces will never be "perfect" but that's the part that makes them one of a kind and reflects the handmade quality of the work.