So the in-laws gave us their blue steel crepe pan they bought at Goodwill after I mentioned that I've been looking to get one. I think it's a De Buyer crepe pan. The problem is they bought it to use as a conductor plate for their portable induction stove, so the middle part of the pan is very discolored. There is also a little bit of sticky residue that seems hard baked on. Searches on the web mostly deal with how to season a pan. Any advice on how to restore a badly/unevenly burnt pan?