Is it permissible Erev Shabos to wrap a pot of rice in a blanket (off the fire/blech) in order to keep it warm?
Answer:
Yes, this is fine. A blanket is classified as an element that is not mosif hevel (does not add heat), and therefore it is permitted to wrap an item of food in it before Shabbos, to keep it warm for the meal.
As the question notes, this applies specifically off the fire; on the fire, the covering is considered mosif hevel, and is therefore not permitted.
