If you’re like most people, you’ve come to rely on your dishwasher to clean a multitude of kitchen items. But despite the convenience and deep cleaning the dishwasher offers, not everything can be safely cleaned there. Here is a list of items that should never be cleaned in your dishwasher:
Your carving and steak knives. Dishwashing detergent can dull the blades over time, and the heat of the water and drying cycle can loosen the handles. To preserve the form and function of these knives, wash them by hand with warm, soapy water.
Certain plastics. If your plastic items don’t say “dishwasher safe,” do not put them in the dishwasher, as they most likely won’t stand up to the heat. Even for dishwasher-safe plastics, put them on the top rack where they’re further away from the intensity of the heat source.
Nonstick cookware. Most nonstick cookware is coated with Teflon, a substance that won’t stand up to the heat of the dishwasher and will, therefore, wear out over time. If you want to keep your omelettes from sticking, wash your nonstick cookware by hand unless the pan specifically says “dishwasher safe.”
Fine china and crystal. The delicate nature of these items makes the dishwasher a hazardous place for them. Avoid damage to the fine finishes of china or chips to your crystal stemware by keeping them out of the dishwasher.
Copper cookware. Popular copper cookware can discolor and get dull in the dishwasher. Instead, wash it by hand with soapy water, then restore its shine with lemon juice, salt and vinegar.
Aluminum cookware. While stainless steel cookware is fine in the dishwasher, aluminum is not, as it can fade and oxidize when exposed to the high temperatures of the dishwasher. Aluminum also doesn’t do well with soaking. Instead, clean it with a mixture of cream of tartar and water. To remove discoloration, simmer a mixture of one tablespoon lemon juice per quart of water on the stovetop.
Wooden utensils and cutting boards. The abrasive nature of dishwashing detergents can damage wooden items over time, and the drying cycle can cause them to warp and crack. To disinfect a cutting board after cutting raw meat on it, clean it with white vinegar or a mixture of two tablespoons bleach in a gallon of water. Rinse thoroughly and dry the board by hand.
Cast iron. Dishwashing detergent will break down the seasoning you created when you first got your cast iron pan, and prolonged exposure to water in the dishwasher will cause it to rust. Instead, rinse your cast iron with a tiny bit of soap or an abrasive such as salt, then dry it thoroughly, leaving it on low heat in the oven or on the burner for a minute or two to thoroughly dry it.
Source: Real Simple Tips