Can rubber be kashered? From what I understand, to be kashered something has to be heated up in boiling hot water, in the case of rubber, I don’t believe it can absorb and retain heat internally. If this is the case, would it be impossible to make a non kosher spatula kosher? Is there a Halacha brought down one way or the other on the issue?
R’ Moshe in Igros Moshe OC 2:92 says that rubber made from trees is able to be kashered but synthetic rubber (silicone, etc) can’t, as it is something new that isn’t found in earlier sources