Dishwasher, Oven, Microwave, and Freezer Safe. Avoid cleaners that may contain citrus. Our Portuguese stoneware ceramics echo the same artisanal production as Juliska glassware. We have developed a variety of exquisite transparent, opaque, and metallic glazes on a tough Portuguese stoneware body. All are lead free and each has the same tough durability to handle the most demanding everyday use.