"As the pan seasons over the uses, it darkens and when it is wiped, the towel turns brownish. This is absolutely normal and it will always be the case.
That is why we advise to wipe iron utensils with a paper towel.
As a result, there is no contraindication in using your iron pan freely and washing it the way you did, that is to say without any detergent."
"The pan gets black over the uses: it is seasoning. The darker it becomes, the less it sticks.
Seal thick pieces of MEAT (especially fat meat) at least 10 times before using the pan to cook anything else."