Graniteware® has long been associated with home food preserving and canning – but not on glass stovetops. Here’s why. For Pressure Canning – some glass stovetops may not produce enough heat/energy required for safe pressure canning. We suggest you do not use a pressure canner on a glass stovetop since there is no way to ensure the required heat/energy production. Our Water-Bath Canners have a slight indentation in the bottom of the pot to prevent warping and flexing under the weight of the water and heat of the stove top. This indentation provides an essential function on standard stovetops, but is not ideal for flat glass stovetops. The indentation can trap air and heat underneath the pot, creating higher than normal temperatures which could cause the glass top to crack. For that reason we do not recommend using the water-bath canners on glass stovetops.