8 Things You Absolutely Should Not Put in a Dishwasher (And Why)
That shattered dishwasher photo is a nightmare! Discover the 8 common kitchen items you should never put in the dishwasher to avoid ruining your appliances and your favorite cookware.
Introduction
If you’ve seen the viral photo circulating online—a dishwasher completely filled with shattered glass shards—you know the horror of a kitchen appliance gone wrong. The caption reads: “My dishwasher suddenly exploded, sending glass everywhere… he told me I should be more careful about what I put in the dishwasher.”
While an “explosion” is rare, the damage dishwashers can do to certain items is very real. We love the convenience of the dishwasher, but it is a harsh environment. Between the scalding hot water, the powerful spray arms, and the alkaline detergents, it’s basically a torture chamber for delicate materials.
To save your favorite kitchen gear (and your sanity), here are 8 things you absolutely should never put in your dishwasher, and the science behind why.
1. Cast Iron Skillets
The Verdict: Never. The Why: Cast iron relies on a layer of polymerized oil (seasoning) to be non-stick and rust-resistant. The high heat and harsh detergents in a dishwasher will strip this seasoning right off, leaving you with a dry, sticky pan that will rust almost immediately.
What to do instead: Hand wash with warm water and a stiff brush, dry immediately, and rub with a little oil.
2. Wooden Cutting Boards and Utensils
The Verdict: Never. The Why: Wood is porous. The intense heat and prolonged exposure to water cause wood to expand and contract rapidly. This leads to warping, cracking, and splitting. Once a cutting board cracks, it becomes a breeding ground for bacteria. The detergent also dries out the natural oils, leaving the wood brittle.
What to do instead: Hand wash with mild soap and warm water. Oil them regularly with mineral oil.
3. Sharp Chef’s Knives
The Verdict: Never. The Why: There are two problems here. First, the high-pressure water jets can bang the knife against other metal items, instantly dulling the razor-sharp edge. Second, the heat can damage the handle (especially if it’s wood or glued), causing it to loosen or crack.
What to do instead: Hand wash gently and dry immediately.
4. Crystal and Delicate Glassware
The Verdict: Never (This is likely what caused the photo above!). The Why: This is the most dangerous category.
Etching: The alkaline detergent is abrasive. Over time, it “etches” the glass, leaving it permanently cloudy and foggy. You can’t scrub this off; the glass is actually damaged.
Shattering: Delicate glass is susceptible to thermal shock. If the water is too hot, or if the glass is knocked by the spray arm, it can shatter into a million pieces—exactly like the photo!
What to do instead: Hand wash gently in lukewarm water.
5. Non-Stick Pots and Pans
The Verdict: Never. The Why: The non-stick coating (Teflon or ceramic) is delicate. The abrasive detergent and the high heat will degrade the coating, causing it to peel and flake off. Once it starts peeling, the pan is ruined and potentially unsafe to cook with.
What to do instead: Hand wash with a soft sponge and mild soap.
6. Aluminum Cookware
The Verdict: Never. The Why: Aluminum reacts chemically with the alkaline detergents used in dishwashers. If you put an aluminum pot in, it will turn a dark, dull gray or black. It can also leave dark streaks on your dishwasher interior and other dishes.
What to do instead: Hand wash. If it gets dark, you can boil apple peels or vinegar in it to restore the color (though it’s difficult).
7. “Good” Plastic Containers
The Verdict: Check the label, but generally avoid. The Why: Unless a plastic container is explicitly marked “Dishwasher Safe,” the heat at the bottom of the dishwasher (near the heating element) will warp and melt it. Even “safe” plastics can become cloudy and brittle over time, and they tend to absorb the smell of the detergent and food.
What to do instead: Hand wash Tupperware and plastic storage containers.
8. Copper Mugs and Pots
The Verdict: Never. The Why: Copper is a soft metal that tarnishes easily. The heat and chemicals in the dishwasher will cause copper to oxidize rapidly, turning it brown or green and ruining its beautiful shine. It can also be toxic if the protective lining is damaged.
What to do instead: Hand wash with a specialized copper cleaner or lemon and salt.
Summary: The Golden Rule
If an item is expensive, sharp, wooden, or delicate, keep it out of the dishwasher. The few minutes it takes to hand wash these items will save you hundreds of dollars in replacement costs—and prevent a glass-shattering disaster!
