I just bought a new lodge cast iron skillet today and used it to cook a Japanese Waghu A5 10+ BMS Ribeye... was worth the hype, yummy.
I washed the Skillet with hot water and salt and then heated it again to dry all the water, but there are some stains left... Do I need to clean this or is this normal and leave it ?
Please see pictures:
But there is some stains left... do I need to clean this or is this normal and leave it ?
As long as the "stain" is hard and dry rather than gummy or sticky, it's probably fine. As commenters have noted, it looks like polymerized oil. You probably cooked your steak at very high heat with some oil in the pan. If you didn't use oil, the stain might just be from some of the fat that rendered out of your well-marbled ribeye. Either way, some of the fat/oil polymerized on the bottom of the pan due to the high heat. This is exactly what you'd do on purpose if you were to season the pan yourself -- coat it in a (very!) thin layer of oil and then stick the pan in a hot oven for a few hours.
As you keep using your pan, it'll acquire a lot of those stains, and it'll eventually be black all over. That's completely normal — it's what a cast iron pan should look like, and the black seasoning is a good non-stick surface.
That looks like oil, from cooking, that was polymerized to your pan. The idea behind seasoning a cast iron pan is to have a polymerized layer of oil evenly coating the interior of your pan. From your description, it doesn't sound like you've seasoned your pan, or maybe, as pointed out in the comments, you did not complete the seasoning. While a well-seasoned cast iron pan can take occasional soap and water cleaning, you probably want to treat a newly seasoned cast iron pan a little differently when cleaning, avoiding soap and water, and just using salt, wiping out, and heating up. If you can remove it, go ahead, then resume the seasoning process. I'm guessing this will be fairly difficult to accomplish. I would continue to season, use, and avoid soap and water for a while.
