Created in 1970 by Corning, Corelle brand dishes enjoy the love of many. Some remember growing up with these kitchen staples while others, attracted by modern patterns, have added the cookware to their own kitchens. Those who have loved their Corelle for many years sometimes notice two types of discoloration. The first issue is rust spots, which are usually limited to the edges of plates, bowls and cups. The second complaint is thin gray lines that most typically appear on plates. Although both problems have different sources, their solution is the same. To get rid of both types of discoloration, Corelle recommends scrubbing your dishes with a nonabrasive cleanser like Bar Keeper's Friend or Zud.
If you have rust spots on your Corelle dishes, the cause is most likely your dishwasher. The racks in most dishwashers are metal and coated in vinyl to protect them from rust. Through time and use, however, this vinyl coating may chip or begin to peel away. When it does, your dishwasher racks start to rust, potentially transferring that rust to your dishes. This typically results in small but noticeable spots of rust on the edges or rims of your dishes. If you wash your dishes by hand and still notice rust on the edges of plates, it's likely time for a new drying rack.
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In addition to rust spots, Corelle users sometimes notice gray lines or markings, particularly on plates. These marks can occur when the dishes rub against metal. The most common cause is the use of serrated metal knives, such as steak knives, on plates. These marks can also occur if your Corelle dishes bump against metal dishes in the dishwasher. To minimize marks, try to avoid using steak knives with your Corelle dishes and load your dishwasher in such a way that metal pots, pans and baking sheets don't bang against your dishes during the wash cycle.
Whether it's rust or gray marks marring your Corelle dishes, the cure is the same. Wet the dish and sprinkle some Bar Keep's Friend or another nonabrasive cleanser onto the discoloration. If a sponge and a bit of elbow grease aren't quite enough, feel free to add a nylon or plastic scrubber to the mix. You can also mix your cleaning powder and some water together to create a paste. Spread the paste on the rust spot and let it work for a few minutes before rinsing it away. Never use abrasive tools like steel wool and other scouring pads, however, as these can cause permanent scratches on your dishes.
Once you've removed the rust stains from your Corelle, consider replacing the racks in your dishwasher. New racks will eliminate rust stains on your dishes. So will washing them by hand, if you're so inclined. If you notice any chips, cracks or severe scratches when cleaning your dishes, stop using the piece and dispose of it. Corelle is extremely strong, but it is glass. Damaged pieces could shatter or break unexpectedly and it is best to discontinue using them. Repaired dishes are as weak as damaged ones, so resist the urge to fix a broken piece.