What Causes Discoloration on Flatware in the Dishwasher?

If you rely on a dishwasher to get your dishes, glasses and flatware clean every day, there are few things more frustrating than finding items stained or discolored after a cycle.

Hard Water

Mineral deposits from hard water can discolor flatware during a dish-washing cycle.Mineral deposits from hard water can discolor flatware during a dish-washing cycle.
In particular, flatware is prone to a variety of discolorations depending on conditions within the dishwasher. All types of flatware, including silver, aluminum and stainless steel, may be affected, and some of the discolorations may be permanent. To prevent spots and marks on your flatware, you must identify the source of the discoloration, so you can adjust your dishwasher habits and keep your knives, forks and spoons shining.

If you live in an area with hard water, you may notice discolorations on your flatware after a cycle in the dishwasher. Hard water contains a high concentration of dissolved minerals. In particular, it usually has a great deal of calcium and magnesium. These minerals can cling to the surface of your flatware and create a discolored film. Connecting a water softener to your home's water supply is the most effective way of dealing with a hard water problem. However, if you don't have a water softening system, make sure to add enough detergent to your loads containing flatware so there is a sufficient amount to rinse away the minerals.

Detergent Problem

The detergent used may also cause discolorations on your flatware. In particular, if you have sterling silver or silver-plated flatware, highly concentrated detergent can cause dark spots on the items if they come into contact with the detergent when they are already wet. To avoid a problem, do not apply detergent directly to your flatware. Instead, pour it into the designated dispenser, making sure to close the cap carefully before starting the cycle. You can remove existing dark spots on your flatware with silver polish and run them through the dishwasher again to get them clean.

High Drying Temperature

Aluminum flatware may become discolored in your dishwasher if the drying cycle features particularly high temperatures. Because aluminum is a softer metal, the excess heat can actually strip its surface. If you suspect the water temperature is discoloring your flatware, do not select the drying option when setting your dishwasher controls. You may also opt to take the flatware out of the dishwasher before the drying cycle begins.

Food Debris

Some types of flatware, including aluminum and stainless steel, may become discolored after exposure to certain food debris in the dishwasher. Foods that are strongly acidic or contain heavy amounts of salt may cause spots on stainless steel software, while aluminum flatware may show signs of discoloration after contact with foods that contain alkalis or minerals. You can remove the marks on stainless steel flatware with silver polish, and use a vinegar solution to get rid of the discoloration on aluminum items. However, you can avoid the marks in the first place by never leaving flatware with food particles on it sitting in dishwasher for a prolonged period without washing it. If you plan to start your dishwasher at a future time, run the rinse cycle to remove stubborn food debris.

About the Author

Based in New York City, Jennifer Blair has been covering all things home and garden since 2001. Her writing has appeared on BobVila.com, World Lifestyle, and House Logic. Blair holds a Bachelor of Arts in Writing Seminars from the Johns Hopkins University in Baltimore, Maryland.