Although today's dishwashers have individual racks and holders to separate everything that goes in them, along with gentle cleaning and drying cycles, modern-day dishwashers are still powerful machines that use high heat, forceful water, and powerful cleaning agents to clean and remove grease and food. Keep in mind that vintage and antique pieces might be irreplaceable, as well. Damage and breakage can happen and no one wants to deal with that expense.
Hot water and the heat from the drying cycle can cause wood items to warp and bend out of shape. And a warped cutting board is really hard to cut on! Hot water can also dull the finish of wood kitchen items. Be sure to hand-wash and air-dry wood items to maintain their beauty and function.
The hot water temperatures that modern dishwashers use can cause crystal to break, chip, and crack. It can also dull the gorgeous finish of crystal items. Crystal is an investment, and you certainly don't want to have your family's heirloom crystal damaged.
It's best to keep Grandma's dishes out of the dishwasher. The color and pattern from vintage and antique pieces can be faded in the dishwasher. The gold parts of any gold-rimmed pieces can also be affected by the high heat and powerful detergents. Gold-rimmed glasses and plates, vintage bowls and dinnerware, and gold-trimmed flatware should only be hand-washed to maintain their beautiful finish and value.
Copper pots and pans and those gorgeous copper mule mugs are best left out of the dishwasher. It's recommended that they be hand-washed with mild soap. Once again, it's the high temperate that is the culprit and can dull copper's shine and finish.
The space between the outer and inner layers of an insulated mug can fill with water if placed in the dishwasher. This compromises its insulating effect.
You've taken the time to perfectly season your skillet -- don't wash away all that yummy flavor! Keeping your cast-iron out of the dishwasher will keep those delicious seasonings in place.
Any items with adhesives, such as bottles and jars that have labels on them, should be kept out of the dishwasher. The labels can clog and damage the dishwasher. The label pieces can be deposited on other items in the dishwasher, too, and cause a mess once dried on.
Some brands of nonstick pans can go in the dishwasher, but if you're not sure of the manufacturer's instructions, it's best to leave them out. The nonstick quality could be affected.
Plastic bottles and containers that are made from soft plastics should not be placed in the dishwasher. The high heat of the cleaning and drying cycles can warp them and make them unusable.
The small holes in graters and microplanes used for zesting and grating cheese, lemons, and limes can be remain plugged when placed in a dishwasher. Ditto any garlic left in a garlic press. It can be almost impossible to clean out those little holes after this happens! These items are best cleaned by hand-washing with a soft-bristled brush.