Regarding kashering a stainless steel sink, why is irui enough when most likely there were hot noodles and macaroni that fell into the sink.
If using irui over a hot stone, how can I tell the stone is still hot enough?
Answer:
Irui is sufficient because the majority of beliyos that entered the sink are by means of iruy and not by hot food actually touching the sink.
For purposes of kashering the Shulchan Aruch (451:6) rules that we follow the majority use of the utensil, and therefore iruy is sufficient.
Although the Rema is stringent on this matter (see Mishnah Berurah 47-8), in the case of a sink the contact of noodles and so on involves the question of a davar gush, which only some authorities consider a keli rishon.
Therefore, for this case we can rely on the opinion that we follow the majority use, and kasher the sink with iruy alone.
If the stone was red-hot, and boiling water is poured on it, we can assume that the stone remains hot enough until it completes covering the given surface.
Best wishes.
