I have a dutch oven I have been using for 30 years. Over the past 2 years or so it has developeda brown deposit on the sides from the bottom up about 1 inch. It does not seem to affect cooking but is unattractive. I use it for many purposes but very often for pot roast. I have a square skillet used primarily to fry chops etc that has developed a similar deposit on the bottom and up the side about 1/4 inch. This is on the inside of both.
What is this and how can I get rid of it?