1. Crystal Glassware: The high heat and harsh detergents will cause crystal to become cloudy, etched, and eventually develop a “milky” film that cannot be removed.
2. Wooden Cutting Boards & Utensils: The intense water pressure and heat will cause the wood to swell, crack, and splinter. It will also strip away natural oils, making it brittle and prone to harboring bacteria.
3. Good Knives (especially Chef’s Knives): The dishwasher’s high heat and harsh detergents can dull and damage the precision-sharpened edge of a good knife. The high-pressure water can also cause the handle to loosen or crack. Handwashing is essential to maintain a good edge.
4. Cast Iron Skillets & Pots: Dishwasher detergent will strip the valuable “seasoning” (polymerized oil) from cast iron, causing it to rust almost immediately. It is very difficult to re-season properly.
5. Insulated Stainless Steel Travel Mugs (like Hydro Flask or Yeti): While the stainless steel itself is durable, the vacuum seal between the double walls can be compromised by the dishwasher’s high heat, destroying the mug’s insulating properties.
6. Graters and Fine-Mesh Strainers: The small holes and sharp edges can trap food particles that the dishwasher’s spray arms may not be able to wash away completely. The high pressure can also dull the grating edges.
7. Plastic Containers Not Marked “Dishwasher Safe”: Low-quality plastics can warp, melt, or release harmful chemicals (like BPA) when exposed to the high heat of a dishwasher’s drying cycle. Always check for the symbol.
8. Disposable Aluminum Foil Pans: The hot, caustic dishwasher detergent will react with the aluminum, causing it to oxidize, turn black, and leave residue on other items in the dishwasher.
8 Things You Absolutely Should Not Put in a Dishwasher And Why
