I have one of those cheap Lodge cast iron skillets. I have only used a small amount of soap on there once when I had some burnt on crud on the bottom. Normally, I just use hot water and a sponge to clean it. But it seems like there is always black residue left behind. I'm assuming this is the preseasoning that Lodge puts on their products. Is this normal or am I doing something wrong? I scrub the devil out of it with hot water and a sponge, but it seems like the black residue will never go away. TIA!