Six generations of Americans have been using Granite Ware canners to preserve fruits and vegetables. The dark porcelain surface and steel core absorbs energy and evenly distributes heat to the contents. The result is a canner that heats rapidly. The canner is perfect for preserving tomatoes or fruit, processing 7 quart jars at a time. Comes with rack for easy lifting jars from canner. Granite Ware's high efficiency, quick boiling performance combined with its modest cost make it ideal for canning. Porcelain enamel is the result of fusing powdered glass to a substrate by firing, usually between 750 and 850 degrees Celsius. The powder melts and flows and hardens to a durable vitreous coating on a carbon steel core. It creates a smooth, hard finish that won’t burn and resists staining. It’s also non -porous so it won’t trap odors or food particles and provides a low coefficient of friction – meaning that it cleans up easily and, it is corrosion and chemically resistant so it will last a long time. When fired, the vessel is placed on pins so the bottom and sides are hardened during the firing process into one smooth laminated glass surface. You may notice slight pin indentations where the glass has flowed around the pin that supports the base during firing. The pin marks do not compromise the finish or performance of the vessel in any way. Can be used on gas or electric stove tops. Not recommended for glass stove tops. 21 1/2 qt capacity.