The dishwasher is the workhorse of the kitchen. Dishes go in dirty and come out clean — day after day. But be careful what you load into your dishwasher, or you may do more harm than good.
We asked Lucinda Ottusch, dishwasher expert at Whirlpool Corporation’s Institute of Home Sciences, for her warnings about what should stay out of your dishwasher. Some of what she says may surprise you...
1. Sharp knives
The dishwasher can dull knife blades, so wash prep knives by hand. Even if the manufacturer's instructions says it's OK to put knives in the dishwasher, you may cut yourself loading and unloading sharp knives, so the safest bet is to hand wash sharp knives.
2. Hollow-handled knives
High temperatures in the dishwasher can melt the adhesive that holds the two pieces of a hollow handled knife together. If that happens, the knife handle will fall apart. Hand wash to keep these in top shape.
Unless the manufacturer specifically states that an item is dishwasher safe, do not put cookware with a nonstick coating in the dishwasher. Over time, the dishwashing process can break down the coating, causing it to flake off during cooking and ruining the nonstick finish.
4. Cast iron
Cast iron should NEVER go in the dishwasher. It takes a long time to build up a nonstick surface on cast iron and dishwashing detergents will strip it away and leave the pan vulnerable to rust. Plain water and nonabrasive sponges are the best cleaners. Take care of cast iron cookware and it can last for many generations.
5. China with metallic decoration
Surprisingly, most porcelain and china dishware is dishwasher safe. But if your dinnerware has metallic images or trim, hand wash it to prevent damage to the decorations. Also, keep in mind that china can get chipped if it accidentally knocks into other dishes during the dishwashing cycle, so load the dishwasher carefully.
6. Antiques and other delicate items
Delicate items such as hand-blown glass, antiques and fine figurines should stay out of the dishwasher. If it’s priceless or a family heirloom, hand wash it.
7. Hand-painted ceramics and stoneware
Unless you want the artwork to go down the drain over time, you should hand wash these items.
Some lead crystal will etch (become cloudy and pitted) after repeated washings. Always follow the manufacturer’s instructions to be safe.
9. Milk glass
Pop semi-opaque milk glass dishware in the dishwasher too many times and that milky white color can turn yellow. Don’t take a chance. Hand wash these items.
10. Gold-colored flatware
Unlike silver, most of which can go in the dishwasher, gold-colored flatware will discolor in the dishwasher.
11. Pressure cooker lids
Never wash pressure cooker lids (including those for stovetop pressure cookers and those for electric types, like the Instant Pot) in the dishwasher as small food particles or dishwasher detergent can collect or lodge in the regulator or safety valves. Instead, wash pressure cooker tops, gaskets and pots by hand in warm, soapy water. Rinse and dry well. Do not store with the top in place as the gasket may seal permanently and you may lose the pot.
12. Brass, bronze or pewter
These metals can become pitted and discolored when washed in the dishwasher. Hand wash to maintain their beauty.
13. Aluminum cookware
The very hot water in dishwashers can stain the surface of aluminum and harsh dishwasher detergents can dull the finish. Even if you don’t care about damaging the looks of flimsy disposable aluminum pie pans, don’t put them in the dishwasher because they can mark nearby items as they move around during the washing cycle. On the other hand, some stainless steel cookware can go in the dishwasher — be sure to check the manufacturer's instructions and rinse the pots and pans well if you are not planning to run the diswasher immediately.
Very hot water can warp or crack the wood and damage the finish on wooden cutting boards and utensils with wooden handles: Hand wash only.
RELATED: How to clean your cutting board
15. Many types of plastic
Unless they're marked “dishwasher safe,” do not put plastic items in the dishwasher. Items that are labeled “dishwasher safe” should be placed on the top rack only. Otherwise, the heating element may melt or warp them.
16. Insulated pitchers, drinkware and travel mugs
The problem here is that high temperatures in the dishwashing cycle could damage the vacuum seal. It’s best to hand wash these.
17. Acrylic dishware
The very hot water and harsh dishwashing products can damage acrylic plates and other dishware, causing hairline cracks and washing away whatever is imprinted on them. Hand wash such items to keep them looking new.
18. Plates you've glued back together
If you've repaired a dish with glue or some other type of adhesive, wash it by hand. The hot water and harsh detergent used in the dishwasher can dissolve adhesives.
19. Printed measuring cups
Measuring cups with measurements printed on the side are best hand washed. Over time, dishwasher detergent will remove measurements on these cups, rendering them useless for measuring.
20. Anything with paper labels
Dishwashers can loosen and remove paper labels from bottles and jars. These pieces of paper can lodge in the drain of the dishwasher or stick on other dishes, creating a messy clean up problem. Remove labels first.
21. Dishes with big pieces of food on them
It might go without saying, but big pieces of food can clog the dishwasher drain or end up on otherwise clean dishes. You don’t have to rinse dishes before loading them in the dishwasher, but you should scrape them.