Overheating is this number one mistake people make when using cast iron. As you can see first hand, cast iron is not as indestructible as everyone claims it is. It can be ruined very easily, especially the antique and vintage pieces. Overheating causes cookware to warp, mainly because the heat being applied does not heat the cookware evenly. Once the bottom bows up, all of the liquid in the pan flows away from the center, to the outside of the pan. That exacerbates the problem more; since, the center of the pan continues to heat, while the outer edges stay cooler due to the pooling of the cooking liquids that need to be evaporated. The opposite happens if the center bows downward. All of the cooking liquid then pools into the center of the pan, and it takes forever to cook what you are cooking, until that liquid is evaporated. Either way, the pan is ruined and unsuitable for proper cooking. We can speculate as to why a pan either bows up or down, but poor cooking results are then end product of both scenarios.
What is really annoying is when you find a skillet with an outer heat ring on it that sits perfectly flat when it is cold, but when you heat the pan, the center bows in either direction as described above, making the pan worthless for cooking. As Duke states, it cannot be undone. It is one more peril to try to avoid when using vintage cast iron for cooking.
See, there really is a method behind the madness of “heavy” current era Lodge. It is so much more forgiving than the old stuff. Sure, you can cook with the old pieces, but you really do need to know how to select that cookware, heat that cookware, and properly cook with it.
The past is the past, it cannot be undone, but we can learn from it, hopefully.
And you thought that your question was long winded.
