How do we handle question of kashering a new material such as silicone. Is it porous or not? Does it have beliah or not? It is neither earthenware nor metal nor glass.

Shalom, Thank you for your question. As you can imagine there is some debate about koshering new materials such as silicone. Rav Moshe Feinstein z t”l, ruled that these types of materials can be koshered (see Igrot Moshe E.H. IV:7) but was stricter when it came to koshering for Pesach (ibid O.C. II:92). The OU rules in line with Rav Feinstein zt”l. There are those that are lenient even for Pesach (and many Rabbis in Israel rule leniently for Pesach). Here is a link to an article on the subject from the OU kashrut organization. https://oukosher.org/content/uploads/2014/07/2014.05-06.pdf Blessings.