Canning Information & Tips Acceptable water bath or pressure canners should not be oversized and should have flat bottoms. When canners do not meet these standards, cooking times may be longer and cooktops may be damaged. On a glass-ceramic surface, the canner bottom should not extend more than one-inch beyond the cooking area. Some canners are specifically designed for use on glass-ceramic cooking surfaces. A special canning element is available for coil surfaces. It elevates the canner which reduces trapped heat. This prevents damage to the porcelain surface and drip bowls. When canning, use the HI heat setting just until the water comes to a boil or pressure is reached in the canner, then reduce to the lowest heat setting that maintains the boil or pressure. If the heat is not turned down, damage to the cooktop may occur. Check with your local Extension Service or a manufacturer of glass jars for the latest canning information.