We detailed the laws relating to hagala of kelim in chapter 10. The operative principle is that the intensity of use dictates the intensity of absorption, but the custom, le-khatḥila, is to kasher everything by means of hagala in a kli rishon (10:6). Therefore, the custom is to kasher cutlery in a kli rishon on the flame even though they absorb principally from a kli sheni. Even if one sometimes uses a fork with something on the fire, since it would be damaged by libun, it may be kashered through hagala, in accordance with the majority of its usage (10:6-7).
Before kashering, one must clean the kelim (10:9). We have already learned how to do hagala in practice (10:11) and how to kasher a large pot that cannot fit into another kli (10:12).
Regarding a skillet, le-khatḥila it is kashered by means of light libun, but one who wishes to kasher it by means of hagala may do so (10:4). A skillet that is normally used without oil – to fry malawach, for example – must be kashered by means of heavy libun (4, n. 3). Non-stick or Teflon skillets cannot be kashered since they are intended for frying without using oil. This means that they must be kashered by means of heavy libun, but since this procedure would ruin them, they cannot be kashered.