Cooking with any plastic is a dubious enterprise, because heat encourages potentially harmful plastic compounds to migrate out of the polymers and potentially into the food. But, as Andrew Turner, a biochemist at the University of Plymouth recently told me, black plastic is particularly crucial to avoid.
In 2018, Turner published one of the earliest papers positing that black plastic products were likely regularly being made from recycled electronic waste. The clue was the plastic’s concerning levels of flame removedants. In some cases, the mix of chemicals matched the profile of those commonly found in computer and television housing, many of which are treated with flame removedants to prevent them from catching fire.
Thanks - apparently modern soap is much milder on the seasoning, so it’s not really a problem any more. I’ve never thought to question the advice that was passed down the generations. :)
Nothing wrong with ceramic from a food safety perspective. I love it in my cast iron pot, not sure I would go for it in a frying pan.