I have read about many different ideas for cleaning the reddish brown mark off the edges of Corelle dinnerware as mine are starting to turn brown. I wash them in my new dishwasher with softened water only and they are still turning brown. Fastest way to do remove this brown discoloration is to put your dish upside down in a plastic cake or pie taker and squeeze Zep toilet bowl cleaner around the edge. Cover and leave overnight. I usually stack a bread plate over a dinner plate then a pie plate, that way I can get three or more pieces done at once. DO WEAR RUBBER GLOVES WHEN YOU DO THIS. They come out white as new.