1. Any Metal That Isn't Stainless Steel
No matter what they are or what you use them to do, you should never place kitchen utensils made of metal that is not steel in the dishwasher.
This includes but is not limited to your cast iron cookware, carbon steel items, nonstick pans and pots, enamel cookware, aluminum cookware, and copper utensils.
If you place any of these inside the machine, they may lose their shine, become darkened, or even start to fall apart over time.
However, remembering these items may be difficult since they are many, so a quick way to remember is to never put any kitchen utensil that isn't stainless steel in your dishwasher.
2. Sharp-Edged Tools
This includes a large variety of sharp kitchen tops like knives graders, scissors, slicers, food processor blades, etc. If you place any of these in your dishwasher, you increase the chances of an unsuspecting person or even yourself, getting cut while unloading the machine.
Aside from that, the potent detergents used in dishwashers will quickly dull the utensils' sharp edges, cause it to rust or damage the handles. Even worse, it may spoil the machine by puncturing the rubberized coating on its racks, which may cause them to corrode.
3. Wooden Utensils
This includes but is not limited to wooden spoons, pots, pans, ladles, and many others. The reason you shouldn't place such materials in your dishwasher is quite apparent – wood is biodegradable!
Because it is biodegradable, it gets easily damaged by moisture and heat. The best way to clean them is by washing manually with as little water as possible and hanging them out to dry completely.
4. Some Plastics
Plastics are generally considered hazardous to human health. It is believed that when they are washed continuously using dishwashers or popped in the microwave, they gradually degrade and produce dangerous chemicals that may be ingested when the utensils are used.
However, this is yet to be confirmed or established as a scientific fact. But, there is no harm in being very careful, especially if you have children who are more prone to the dangers of hazardous chemicals.
5. Fragile Plates, Delicate Glassware, Fine China
Delicate kitchen utensils shouldn't be placed in a dishwasher because they might be too delicate to withstand the washing cycle.
Considering that these are usually expensive, there is no need to risk the machine breaking them, so wash them by hand.
6. Anything Mechanical
This includes parts of small machines you use in your kitchen, from hand rollers to pressure cooker lids; these should never be placed in the dishwasher if you want them to last long.
Instead, follow cleaning instructions from the manufacturer.
7. Utensils With A Hollow Handle Or Thermal Insulation
Any such items like whisks, scoops, or thermos bottles are not fit for a dishwasher. Water may get into the hollow space of any utensil and subsequently cause rust or even more extreme results like an explosion of the handle caused by pressure.
8. Natural Stones, E.g., Granite
Natural stones are frequently used to make slates, mortars, and pestles. After use, the best way to clean these is by washing and drying by hand.
If placed in the dishwasher, detergents can damage the glossy finish, and exposure to high heat and lots of water may cause it to crack.
On a final note, don't even think about using your dishwasher as a quick shortcut to getting strange things like your bras, engine parts, or keyboards clean! No, never.