Hagalah with steam

Hi,

One cannot kasher via hagalah with steam alone, regardless of its heat, since it is not clear that the steam will cause absorbed taste to be extruded. However, where the steam comes from water at a high boil, and it causes significant quantities of water to develop on the surface, that suffices.

(Rav Moshe Feinstein, Igrot Moshe Yoreh Deah 1:60)

Have a great day,
Mordechai