The dishwasher is one of the most convenient appliances in the modern kitchen, taking the hassle out of cleaning and giving us more time for what matters. But as tempting as it may be to toss everything into the machine, not all items are built to withstand the heat, water pressure, and harsh detergents inside. In fact, some things can be permanently damaged after just one cycle.

To help you protect your favorite kitchen tools and extend their lifespan, here are 10 items that should never go in the dishwasher — and why they require gentler care.

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1. Wooden Utensils — They Warp and Crack

Wood absorbs water easily. In the dishwasher, wood swells from moisture, then shrinks as it dries, causing warping, cracking, and loss of its natural oils. Hand-wash wooden spoons, spatulas, and cutting boards with mild soap, then dry them immediately.

2. Cast Iron — Seasoning Gets Destroyed

Cast iron relies on its seasoning layer for a nonstick surface. Dishwashers strip this layer away, leaving the pan vulnerable to rust. Clean cast iron with hot water and a brush, dry completely, and add a light coat of oil.

3. Sharp Knives — Blades Become Dull

Dishwashers knock knives around, dulling their blades quickly. Heat and detergents also damage the metal. Hand-wash knives and dry immediately to maintain sharpness and prevent rust.

4. Nonstick Pans — Coating Breaks Down

High heat and strong detergents wear away nonstick coating, causing flaking and reducing the pan’s effectiveness. Wash gently with a soft sponge and mild soap to extend its life.

5. Crystal Glassware — Prone to Etching

Crystal is delicate and reacts poorly to dishwashing detergents and high temperatures, which can cause cloudy etching or even cracks. Hand-wash crystal to preserve its clarity and brilliance.

6. Insulated Mugs — Vacuum Seal Can Fail

Dishwashers can weaken the vacuum seal that keeps drinks hot or cold. When that seal breaks, the mug loses its insulating power. Hand-wash and air-dry with the lid off.

7. Aluminum Cookware — Discoloration and Pitting

Dishwasher detergents cause aluminum to oxidize, turning it dull and gray. Over time, pitting can occur. Wash aluminum cookware by hand to maintain its appearance and performance.

8. Gold-Plated Dishware — Fades Quickly

Gold plating is thin and can easily be stripped by detergents and high heat. Hand-wash gold-trimmed plates, bowls, and utensils to prevent fading and tarnish.

9. Copper Pots and Pans — Tarnish and Warping

Copper reacts strongly to dishwasher detergents, losing its shine and forming tarnish. Heat can also warp the metal. Clean copper by hand with a gentle cleaner or lemon-and-salt mix.

10. Hollow-Handled Knives — Handles Loosen

The adhesive inside hollow-handled knives softens in dishwasher heat, causing the handle to separate from the blade. Hand-washing keeps them sturdy and safe to use.

11. Soft Plastics — Warp or Melt Easily

Lightweight plastic lids and containers can warp under high heat, making them impossible to seal. When in doubt, wash soft plastics by hand.