• Cast-iron, enameled-cast-iron, and copper pots and pans are on the never list. Why? Cast iron rusts; enameled cast iron chips; copper dents.
  
• Formal dishes and nice flatware can get worn with repeated washings. Rule of thumb: If it’s something you would cry over harming or losing, don’t put it in. (If you do put sterling silver in the dishwasher, use about a tablespoon of detergent and don’t mix it with stainless-steel flatware; a chemical reaction between the metals can discolor the silver.)
  
• Wooden spoons can warp and crack. If you don’t mind replacing them frequently, throw them in; otherwise wash them in the sink.
  
• Good kitchen knives and steak knives aren’t cheap. Why risk dulling their blades?
  
• Crystal glasses are especially vulnerable. Food particles can etch them; heat can cause cracks. After hand washing (it’s usually safer than using the china/crystal setting), dry with a cloth that hasn’t been laundered with fabric softener, which can leave a film.
  
• Insulated mugs and containers feature vacuum seals, which can be destroyed if water seeps in.
  
• Brass items should never see the inside of a dishwasher. Hot water can remove the natural protective layer that forms on brass.
  
• Wooden cutting boards can swell and contract, leaving them teetery and essentially useless on a counter. Most bamboo boards are susceptible, too. But we found one that uses a heat-resistant adhesive, making it dishwasher-safe: Totally Bamboo GreenLite collection, $11.50 to $40, totallybamboo.com.

—Mohandas K. Gandhi