If you leave the oven cleaner on too long, it will start to turn the aluminum black. Unless you leave the oven cleaner on for over 10 minutes, the black can easily be removed with the polish. If you don't like how it turned out after using the oven cleaner, go over the whole chassis with 1000 grit sand paper, then polish. I hand polished that chassis for an hour to get it to shine that well.