Stainless steel pan

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.

Had a warped stainless steel pot I was getting ready to toss, but decided to give it one more use since I forgot it was warped until I needed to use it right away. Was making tamales so it was on a good simmer for about 3-4 hours. Placed a heavy cast iron Dutch oven on top while it cooked to try to get better contact with my ceramic top stove. Left it to cool and forgot about the pot until I went to clean it in the morning. When I did, I noticed the warp was all gone. Pleasantly surprised and glad I did t throw it away. I will definitely be more careful with it in the future. Hope this is helpful to someone out there.