Putting items that are not dishwasher safe in the wash, such as cast iron, nonstick and aluminum pans, sharp knives, wooden boards, insulated mugs and thin plastic, damages the items and can stain or scratch the dishwasher's racks. Anything without a dishwasher-safe marking belongs in the sink, and rust-prone tools belong nowhere near the racks.
Mistakes at a glance
| Habit | What it leads to | Do this instead |
|---|---|---|
| Washing cast iron or enameled cast iron | Stripped seasoning, chipped enamel and rust that can stain the racks | Hand wash and dry right away |
| Putting nonstick pans or most aluminum in | Damaged coatings and discolored aluminum | Hand wash unless the maker says otherwise |
| Washing good sharp knives | Nicked, dull blades and gouged rack coating | Hand wash and dry knives |
| Washing wooden boards and wooden-handled tools | Swelling, warping and cracks | Hand wash and let them air-dry |
| Putting insulated travel mugs and lids in | Damaged seals and insulation | Hand wash unless marked dishwasher safe |
| Running thin or disposable plastic | Melting or warping | Top rack only, and only plastic marked dishwasher safe |
| Washing crystal, hand-painted, metal-rimmed or antique pieces | Etching, fading or breakage | Hand wash delicate and heirloom items |
| Washing copper pots or mugs | Pitting and discoloration | Hand wash copper |
The ones that matter most
Cast iron, nonstick and aluminum
High heat, strong spray and dishwasher detergent are hard on cookware finishes. Whirlpool says cast iron, enameled cast iron, nonstick and most aluminum pots and pans should never go in the dishwasher, because the heat and detergent remove the oils that season cast iron, damage or remove nonstick coatings, chip enamel and discolor aluminum. Cast iron causes a second problem: Maytag notes that rust-prone items such as non-seasoned cast iron can leave brown stains on the racks, and that heavy items like cast-iron skillets can scrape the coating off the rack tines.
Knives and wood
Whirlpool says to avoid putting sharp knives in the dishwasher because the blades can get nicked or dull, and that the heat and humidity can make wooden cutting boards and wooden handles swell, warp or crack. Maytag adds that steak knives and other sharp tools can gouge the vinyl coating on the racks, which then lets the metal underneath rust.
Insulated mugs and thin plastic
Travel mugs look sturdy, but Whirlpool warns that water and heat can damage their seals and insulation. Thin or disposable plastic can melt, and acrylic and melamine can crack and fade. GE Appliances lists dishwasher-safe plastics among the items that belong on the top rack. Plastic that melts can drip into the tub, so keep anything flimsy out entirely.
Delicate glass, china and copper
Crystal, hand-blown or painted glass, milk glass, and anything antique, metal-rimmed or hand-painted should be hand washed to avoid breakage, etching or fading, according to Whirlpool. Copper should also be hand washed to avoid pitting and discoloration. Whirlpool also points out that there is no industry standard for what counts as dishwasher safe, so check the marking on the item or its maker's instructions. Loading the items that do belong in the dishwasher is covered in dishwasher loading mistakes that lead to dirty dishes.
Signs it's already caused a problem
- Brown rust stains on dishes or on the rack tines
- Chipped or peeling coating on the racks
- Melted plastic stuck to the tub floor, the filter or the lower rack
- Cloudy, etched glassware that doesn't come clean
- Warped containers or lids that no longer fit
Melted plastic on the tub floor or a damaged rack may need a technician or a replacement part. ProFix San Antonio serves homes in New Braunfels as well as San Antonio and Bexar County.
Sources
- Whirlpool: What Is and Is Not Dishwasher Safe
- Maytag: Tines are Chipped, Scratched or Damaged, Dishwasher
- GE Appliances: How to Properly Load a GE Dishwasher
Habit to keep: Check the care instructions on new cookware, knives and travel mugs before their first wash.
If plastic has melted in the tub or the racks are rusting, call ProFix San Antonio at (210) 761-6006.