Throughout the year, people usually use the same stovetop grates for both meat and milk, because even if some meat or dairy food spills onto them, the flame incinerates and befouls whatever has spilled. However, people customarily perform light libun on such grates for Pesaĥ, because of the seriousness of the ĥametz prohibition (Rema 451:4; MB ad loc. 34). Alternatively, one may wrap thick aluminum foil around the bars on which pots sit, so that there is a barrier between the Pesaĥ pots and the parts of the grates that came into contact with ĥametz. Be-di’avad, the food remains kosher even if cooked on grates that did not undergo libun.
The areas of the grates that do not come into contact with the pots, the enamel cook top beneath the grates, and the burners must be cleaned well of all residual food. Since none of these parts come into contact with the pots, they need not undergo libun or be covered with foil. Generally, people turn on all the flames for half an hour.
It is also important to know that throughout the year one should be stringent and refrain from eating food that has fallen onto the enamel cook top under the grates, because meat and dairy foods spill there, and the enamel becomes not kosher. If one knows that the enamel has been cleaned thoroughly and that no meat and dairy foods have spilled on it in the past twenty-four hours, one may eat what falls there. But when these two conditions have not been met, one should be stringent and refrain from eating whatever comes into contact with this enamel, because it might have absorbed the taste of meat and milk. If a thick piece of food falls there, one may cut off the side that has come into contact with the enamel and eat the rest.
Electric ranges: Clean thoroughly and run on the highest setting for half an hour.
Ceramic burners: These look like smooth and unbroken glass surfaces on which pots are placed directly. They are koshered by cleaning and then heating on the highest setting for half an hour, based on the principle of ke-bole’o kakh polto.
. Throughout the year, we cook both meat and dairy pots atop the grate because taste is not transferred through dry metal. For example, if a hot meat pot touched a hot dairy pot, as long as both pots were dry in the spot that they touched, both pots are kosher. Similarly, even if the grate absorbed the taste of meat, once it dries the taste does not transfer to a dairy pot. Even if a drop of dairy spilled onto the grate in the same spot that meat liquid had previously spilled, the pot remains kosher, since the flame is constantly heating the grate, and whatever liquid had previously spilled on it has already been incinerated. Due to the stringent nature of the ĥametz prohibition, light libun is required but not heavy libun, since technically the grates need not be koshered at all. Kaf Ha-ĥayim 451:82 (citing Ma’amar Mordechai) concurs that le-khatĥila grates should undergo libun, but be-di’avad they are not prohibited. Ĥazon Ovadia p. 75 states that hagala is sufficient to kosher grates, but SAH maintains that light libun is necessary. I believe that covering the grates with aluminum foil is as effective as light libun and perhaps even heavy libun, since it completely separates the grate from the pots, so that even if some liquid spills, it would not connect the grate and the pot.