Here is my one month old De Buyer pan:
I've seasoned it off and on in the last month at least 10 times, using thin layers of oil and on the stove top. It's very dark brown to black over the entire cooking surface. This is my first pan that requires seasoning (carbon steel or cast iron) so I'm just feeling my way in the dark here.
I had some initial traumatic experiences with bacon. The "internets" claim that bacon is fatty and great to break-in a newly seasoned pan. Lies. Lies. The sugar in bacon burnt into the pan and I had to boil water to remove the stains, which took some seasoning away. Since then I've cooked eggs, pancakes, Kartoffelpuffer, char kway teow, and caramelized steak with great success. I'm finally starting to feel this pan is living up to the hype.
After charring some sous vide steaks over high heat this morning, I noticed black splotches on the pan:
I've cleaned the pan (water, brush, plastic scrubby) probably more than I should already, so this is not something that can be cleaned off. That makes sense as the high heat used to char the steaks is very similar to a seasoning session. It's just uneven.
Is this (making the pan bottom slightly uneven) a problem? Is this to be expected? Is this the type of thing repeated ad infinitum that makes heirloom cast iron so valuable?