Carbon steel and cast iron cookware have reactive metal surfaces that will rust if left exposed to moisture and air, especially when heated. To use these materials of cookware you need to season them which involves washing the surface clean and applying a very thin layer of oil which you then heat up to a high temperature (usually past the smoke point, but not strictly necessary).

The heating of oil in contact with the metal causes the oil molecules to polymerize and bond to the metal surface. Done properly, this gives your cast iron and carbon steel cookware a smooth, glassy, slightly brown protective polymer layer which prevents rust and helps foods release (though not as well as nonstick pans). The seasoning process can be repeated as many times as you like and it builds up more and more layers which darken over time. A well seasoned piece of cast iron or carbon steel cookware will look shiny and jet black, though this is not necessary for cooking.

The downside of these materials is that acidic or basic foods can damage the polymer layer and dissolve it right off the pan with enough heat and cooking time. Tomato sauce is a classic example of an acidic food that will eat away at the seasoning of a cast iron or carbon steel pan. A well seasoned pan can still be used to cook a tomato sauce, but not one you plan to be simmering for hours and hours (like some Sunday meat sauce like you’d see in Goodfellas).

Stainless steel (as well as enameled or porcelain coated) cookware is nonreactive so you can use it to cook acidic or basic foods no problem!

SO THAT IS WHY MY FRYING PAN IS ANNOYING!

I just thought it was going to be naturally ground down over time...

Damn it, now I gotta find a thrift store.

Sorry if this is a dumb question, but why would you use it to melt lead?

Sigh, just when I thought I found a way to get a smooth frying pan, look in my comments, I litterarly just posted here....

Why would people melt lead in a frying pan?

Fair, but you can get a lead testing kit for around $10 USD.

Likely, if we’re being honest.

Health agencies haven’t done that much investigation (wheeeee regulatory capture) into wtf microplastics do in nuance to all of our various biological systems, but we do know that microplastics basically pervade everything at every level of the food chain at this point. So it’s more about answering the question of “how much did we fuck ourselves” now.

That article basically confirms my understanding of the safety implications of PTFE. Don't overheat, and discard once flaking, but ingesting flakes is unlikely to be harmful.

I've started favouring other types of cookware as well - my personal favourite is enameled cast iron - but I'm really not keen on using neither cast iron nor carbon steel. I feel like proponents downplay the increased maintenance that comes with that type of cookware.

I do have one ceramic non-stick pan that is pretty good, but once it goes bad I'm probably going to try to find an enameled cast iron replacement for it.