I have a Mauviel 1830 carbon steel pan. It's a couple of years old but I haven't used it for a while. I've used it a few times recently and while it cooks, I think it needs serious maintenance. The picture shows the pan, after having been washed. I think the center is fine but I don't like the heavy black deposit around the outer bottom. I put a bit of oil on the heavy black parts, rub with paper towel and the paper turns black. This doesn't seem right. The pan feels completely smooth. I've tried to remove the black deposits with no luck. Any advice, suggestions ... greatly appreciated.