8 Things You Should Never Put in the Dishwasher (And Why)
A dishwasher is a convenient way to clean many kitchen items, but not everything is designed to withstand high heat, strong detergents, and powerful water jets. Putting the wrong items inside can cause damage, reduce their lifespan, or even create safety issues.
1. Wooden Utensils and Cutting Boards
Wood can absorb water and expand, then shrink as it dries. The repeated heat and moisture of a dishwasher may cause:
- Cracking
- Warping
- Splitting
- Damage to protective finishes
Better option: Hand wash wooden items and dry them promptly.
2. Cast Iron Cookware
Cast iron relies on a protective seasoning layer that prevents rust and creates a naturally nonstick surface. Dishwasher detergents can strip away this layer, leading to:
- Rust
- Dull surfaces
- Reduced cooking performance
Better option: Clean cast iron with warm water and gentle scrubbing, then dry and lightly oil it.
3. Sharp Knives
Dishwashers can dull knife edges because:
- Water jets can knock blades against other items.
- Heat and detergent may damage handles.
- Improper loading can create a safety hazard.
Better option: Hand wash knives and dry them immediately.
4. Nonstick Pans
High heat and harsh detergents can gradually damage nonstick coatings, causing them to:
- Wear down faster
- Lose their smooth surface
- Potentially peel over time
Better option: Follow the manufacturer’s cleaning instructions—many nonstick pans last longer with hand washing.
5. Crystal Glassware
Delicate crystal may be damaged by:
- High temperatures
- Strong detergents
- Movement during washing
This can lead to cloudiness, scratches, or cracks.
Better option: Hand wash valuable or delicate glassware.
6. Copper Cookware
Dishwasher detergents can affect copper’s finish and cause:
- Discoloration
- Loss of shine
- Surface damage
Better option: Clean copper by hand using appropriate methods.
7. Insulated Travel Mugs and Thermoses
Many insulated containers are not dishwasher-safe because heat and water pressure may damage:
- Vacuum seals
- Insulation layers
- Protective coatings
