Cleaning – What is the Dark Gray Residue Coming off the Sheet Pan after Scouring?

This happens to mine, and they are most definitely stainless, not aluminum. Our stainless sink gets the same way. I assume it's from all the minerals in our water. I have found that mixing up some Oxyclean and water and a couple of minutes' soak and a scrub with a plastic scrubber will get rid of it (both from the pan and from the sink). It comes right back, though.

I haven't found that it has any negative impact on the usability of the pans, and doesn't shorten the life significantly if the 14+ year old chef's pan I use almost daily is any indication.

I did a little more research, and it's definitely mineral haze. Recommended treatments are Barkeeper's Friend (mild oxalic acid) soak/scrub, or boiling some vinegar, either one followed by a thorough rinse. In theory, if the haze is left alone it could develop into buildup, which would begin to degrade performance, but in practice it's not an urgent worry.

So if it bugs you, clean it off with mild acid or oxygen bleach. But expect it to come right back. If you only removed it once a year, you'd be a couple of years ahead of my cleaning schedule, and I haven't seen any harm from it.

If all the seasoning is completely removed, it will look shiny like brushed or polished metal. This takes a lot of time, and often power tools. I would first ask whether this is what you want to do: does the pan feel waxy, and have a surface that turns glossy when heated? Then there is wax which can be easily removed with a scrub-brush while water is boiling in the pan. Finish with a little soap and hot water, and you're ready to season.

If it is, in fact, the seasoning you want to remove (if, for example, it is coming off in places, or parts are rusting, typically on cookware which has been left outside), the easiest procedure is to heat the pan very hot, either in the coals of a campfire, or in an oven on 'clean' to burn off the previous coating (don't do this with a pan coated in wax, the wax will burn and smoke), then brush with steel wool until the metal pan starts to show through. You will need to season with several coats of an oil like crisco or coconut, and this will take a lot of time. It's rarely necessary to strip a pan unless it is in awful condition.

At the point you're at, I'd assume that any wax or residue is gone from your work with the steel wool, and that you don't need to go as far as to strip the whole thing. To salvage it, put aside the steel wool, scrub with a plastic brush and hot water until the black residue is gone. Clean a little more using a rag and oil (which will pick up oil-soluble debris) until that is clear. Then season as you normally would, using a light oil like crisco in the oven.