The article is a bit confusing being its referring to used cookware... I don't know or understand enough about the topic, however iirc (I spoke to the Cor briefly) the psak is from R Shlomo Miller. It seems that most oils used by companies who make these use kosher vegetable oil, however I was told even if kosher oil wasn't used it would still be fine. I don't know the rationale.
What do you mean by the article referring to the seasoning? What else would be an issue?
This is the response I got from the COR
Hello,
New cast iron does not require koshering. The oils that are applied are liquid, and therefore even if treif oil was used it would require hagalah or libun kal. They are already subjected to libun kal by the manufacturing process.
Used cast iron- if a pan that can hold liquid, we consider rov tashmisho with liquid, and rely on a self clean oven to kasher.
If it was used without any liquid, it requires libun chamur lchumra- by burying in coals. Another eitza I mentioned was heating to its highest temperature and then using a blow torch to raise the temperature to get red-hot, in all areas.
Kol Tuv,
Rabbi Yechiel Teichman
Rabbinic Coordinator
