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    Things You Should Never Put in the Dishwasher

    Is cast iron off-limits? What about wooden spoons? I'm here to dispel any confusion you might have about which materials are dishwasher-safe.

    Knife, cast iron pan and cutting board on black background. Photo: Getty Images

    I have a different relationship with each of my kitchen appliances. With the fridge, I feel a friendly familiarity, and with my microwave, a sort of unspoken camaraderie. I interact with both frequently, sometimes several times a day.

    With dishwashers, though, there is a reverence. My family didn’t own one until I was much older, and it has always seemed like a mysterious invention to me. Every time I use one now, I’m worried about doing something wrong, specifically whether I’m putting in an item that I shouldn’t. If you’ve ever had similar worries, here’s what you should know.

    Things You Should Not Put in Your Dishwasher

    Acrylic dishware or accessories: Crazing (small cracks through the acrylic) might occur.

    Brass, bronze, copper, and pewter items: High-temperature water and detergent can cause discoloration, says Larry Ciufo, who has tested hundreds of dishwashers at CR over the past 20 years.

    More on Dishwashers and Cookware

    Cast-iron cookware: You risk removing the seasoning—the baked-on oil in your pan that helps prevent food from sticking—which can cause the pan to rust. (See our review of the best cast-iron frying pans.)

    Insulated mugs: Unless they’re labeled as dishwasher-safe, water can get inside the seal between the inner and outer layers of these mugs, which might affect their ability to retain heat or keep drinks cold. (See our review of the best insulated cups.)

    Nonstick pans: If the manufacturer doesn’t say it’s dishwasher-safe, avoid putting them in the dishwasher because the washing process could wear away the coating, Ciufo says. (See our review of the best nonstick frying pans.)

    Sharp knives: Even if they’re labeled dishwasher-safe, you should wash them by hand because they can get dull after rubbing against other cutlery in the basket. (See our review of the best chef’s knives.)

    Tin items: Tin will rust if washed in the dishwasher, so you should hand-wash and dry them immediately. 

    Wood: Water and heat can result in your wooden salad bowls or cutting boards warping and cracking.

    Things That Are Generally Safe, but With Caveats

    Aluminum is usually dishwasher-safe, but minerals in the water might cause spots or darkening. To remove those, scour with a soap-filled steel wool pad.

    China, crystal, and stoneware are mostly safe, but if the pieces are hand-painted or fragile, wash them by hand. It’s also better to hand-wash glasses or dishes with gold leaf.

    Milk-glass items might yellow after repeated washings in the dishwasher.

    Plastic items vary in their ability to withstand heat and detergents, so check whether they’re dishwasher-safe and make sure to place them on the top rack—away from the heating element—and don’t select cycles that use higher wash or dry temperatures.

    Stainless steel and silver are generally okay to put in the dishwasher, but make sure you run your rinse cycle if you’re not running the wash cycle immediately, because prolonged contact with food can damage their finish.

    @consumerreports

    Not everything you may use in the kitchen is suitable for dishwashers. For expert tips and dishwasher reviews, tap the link in our bio. #cleantok #cleaningtiktok #dishwasher

    ♬ original sound - Consumer Reports

    Pang-Chieh Ho

    Pang-Chieh Ho is a senior content creator at Consumer Reports who writes about the intersections of home products and health. She has been working in the media industry for almost 10 years. Books are her first love, but movies come a close second. You can send tips to her at pangchieh.ho@consumer.org.