Your dishwasher is a workhorse, but it’s not invincible. Tossing the wrong item in can ruin your cookware, your cutlery, and even the machine itself. This guide walks you through the items that should never see the inside of a dishwasher, what happens if they do, and how to handle the aftermath. Before you load your next rack, take a quick look at this list—it’ll save you money and frustration.
What You’ll Need
- Your dishwasher’s manual (to check specific cycles and settings)
- Mild dish soap and a soft sponge for hand-washing
- A dry, soft cloth for immediate drying of delicate items
- White vinegar and baking soda (for cleaning the dishwasher itself, if needed)
Step-by-Step
- Check the material before you load. Look at the bottom of pots, pans, and dishes for a dishwasher-safe symbol (usually a cup and glass icon). If you see the words “hand wash only” or “not dishwasher safe,” keep it out. When in doubt, hand-wash.
- Keep wooden items out. Wooden cutting boards, spoons, salad bowls, and any utensil with a wooden handle will absorb water and detergent. The heat and moisture cause the wood to crack, warp, and lose its finish. Over time, the wood can split, creating hiding spots for bacteria. Wash these by hand with mild soap and warm water, then dry immediately.
- Remove knives and sharp tools. Quality kitchen knives—especially those with high-carbon steel blades—will dull quickly in the dishwasher. The harsh detergent and the jostling against other items can nick the blade and damage the handle. Also, the pointed tips are a safety hazard when you’re unloading. Hand-wash knives with the blade facing away from you, and dry them right away.
- Keep nonstick pans out. The dishwasher’s high heat and strong detergents can break down the nonstick coating, causing it to peel or flake. Once that happens, the pan is no longer nonstick and may release chemicals into your food. Even if the pan’s label says “dishwasher safe,” it’s safer to hand-wash to extend its life.
- Don’t put cast iron or carbon steel in. These metals are seasoned with oil to create a natural nonstick surface. The dishwasher’s detergent strips that seasoning, and the water causes rust. You’ll end up with a rusty, sticky mess. Hand-wash with hot water and a stiff brush (no soap unless you plan to re-season), then dry thoroughly and rub with a thin layer of oil.
- Keep aluminum items out. Aluminum pots, pans, and baking sheets can discolor and pit in the dishwasher. The alkaline detergent reacts with the metal, causing a dull, gray film. If you have anodized aluminum, the coating can be damaged too. Hand-wash aluminum with mild detergent and dry immediately.
- Remove delicate glassware and crystal. Fine crystal, etched glass, and hand-painted glass can become cloudy or lose their pattern in the dishwasher. The heat and detergent can also cause tiny fractures. If you have guests’ good glasses, wash them by hand with a gentle detergent and a soft cloth.
- Keep plastic items out unless marked. Thin plastic containers (like takeout containers) can melt or warp, releasing chemicals into your dishwasher. Even thicker plastics may not withstand the heat. Check the bottom of the container for a “dishwasher safe” label. If it’s not there, hand-wash.
- Don’t wash insulated mugs and bottles. Many insulated travel mugs and water bottles have a vacuum seal that can be broken by the dishwasher’s heat. This ruins their insulating ability. The high heat can also damage the plastic lid and the rubber gasket. Hand-wash the lid and the bottle with warm soapy water, and let it air dry.
- Keep copper and brass out. Copper and brass items will tarnish and may develop a greenish patina in the dishwasher. The detergent is too harsh for these metals. Hand-wash with a mild soap and a soft cloth, then polish as needed.
- Don’t put heirloom or vintage dishes in. Older dishes may have lead-based glazes or gold/silver trim that can be damaged by the dishwasher. The heat and detergent can cause the trim to fade or the glaze to crack. If you’re unsure, hand-wash.
- Keep out anything with adhesive labels. Jars or containers with paper labels will have the labels peel off, clogging the dishwasher’s filter. Remove labels before washing, or hand-wash these items.
Common Mistakes
- Assuming “top rack only” means safe. Some items are only safe on the top rack, but that doesn’t mean they’re safe at all. For example, some plastics are only safe on the top rack but still may warp if the heat is too high. Always check the manufacturer’s instructions.
- Putting silverware with stainless steel. Mixing different metals can cause a reaction that pits or discolors the silverware. Keep them in separate baskets or wash them by hand.
- Using the “heated dry” cycle for delicate items. Even if an item is dishwasher safe, the heated dry cycle can be too harsh. Use the air-dry or eco cycle instead.
- Overloading the dishwasher. When you pack too many items, they can knock into each other, causing chips and cracks. Follow the manufacturer’s loading guide.
Tips
- Read the manual. Your dishwasher’s manual will tell you which cycles are best for which items. Some have a “china” or “gentle” cycle that is safer for delicate items.
- Hand-wash in batches. If you have a few delicate items, wash them by hand right after use to avoid buildup. It’s easier than scrubbing later.
- Dry immediately. For items that you hand-wash, dry them with a soft cloth to prevent water spots and rust.
- Use a rinse aid. A rinse aid helps water sheet off dishes, reducing spots and film. It’s especially helpful for glassware.
- Clean your dishwasher regularly. Run an empty cycle with a cup of white vinegar on the top rack to remove mineral buildup and odors. Then sprinkle baking soda on the bottom and run a short cycle to freshen.
Troubleshooting
What if I accidentally put a wooden spoon in the dishwasher? If it’s already been through a cycle, check for cracks or warping. If it’s still intact, you can sand it lightly and re-oil it with food-grade mineral oil. If it’s cracked, discard it.
My nonstick pan has a white film after being in the dishwasher. This is likely detergent residue. Hand-wash the pan with warm soapy water and a soft sponge. If the coating is peeling, it’s time to replace the pan.
My glassware is cloudy. This is often caused by hard water and detergent film. Try washing a glass with a bit of white vinegar. If that doesn’t clear it, the glass is etched and can’t be fixed. To prevent it, use a rinse aid and avoid the heated dry cycle.
The dishwasher smells bad after washing something I shouldn’t have. Run an empty cycle with a cup of white vinegar in a dishwasher-safe cup on the top rack. If the smell persists, check the filter for food debris and clean it out.
My cast iron pan is rusted after a dishwasher run. Scrub off the rust with steel wool, wash with hot water, dry completely, and re-season with oil. It may take a few coats to get it back to nonstick.
Frequently Asked Questions
Q: Can I put my stainless steel pots in the dishwasher?
A: It depends. Some stainless steel is dishwasher safe, but the detergent can dull the finish and cause water spots. Check the manufacturer’s label. If it’s not marked, hand-wash to be safe.
Q: Is it okay to wash plastic baby bottles in the dishwasher?
A: Only if they are marked “dishwasher safe” and you use a gentle cycle without heated drying. The heat can degrade the plastic over time. Many parents prefer to hand-wash to avoid any risk.
Q: Can I put my coffee mug with a ceramic design in the dishwasher?
A: If the design is painted on top of the glaze, it can fade or crack. If the design is under the glaze (like most commercial mugs), it’s usually safe. When in doubt, hand-wash.
Q: What about my good china?
A: Unless it’s marked “dishwasher safe,” don’t put it in. The heat and detergent can damage the glaze and any metallic trim. Hand-wash with a mild detergent and dry immediately.
Q: Can I wash my thermos in the dishwasher?
A: No, the heat can break the vacuum seal and ruin the insulation. Hand-wash the inside with warm soapy water and a bottle brush, and wipe the outside with a damp cloth.
Q: Why does my dishwasher leave a film on my dishes?
A: This is usually due to hard water or too much detergent. Use a rinse aid and reduce the amount of detergent you use. If the film is on glassware, it may be etching, which is permanent.