Surprising Things You Should Never, Ever Put in the Dishwasher

Think you know your way around the dishwasher? You probably turn to this useful appliance to save time. But a dishwasher isn’t foolproof.

In fact, you can make plenty of mistakes each time you load your dishwasher. And if you aren’t careful, you might be loading your dishwasher with items that are pretty likely to get ruined once you hit that “wash” button. We all want to save time but not at the expense of a good set of knives or that copper cookware you saved your pennies to buy.

Read on to check out some of the most surprising things you shouldn’t put in the dishwasher.

1. Cast iron

iron pan

Don’t ever put cast iron in the dishwasher. | iStock.com/YelenaYemchuk

While a pro knows you should never put a cast iron skillet or dutch oven in the dishwasher, not everybody got that memo. Cast iron cookware is seasoned with oil to prevent it from rusting. A spin in the dishwasher strips that oil away, leaving your cookware vulnerable. Instead, Good Housekeeping recommends rinsing your cast iron with warm water and rubbing it clean with salt. That way, you won’t ruin that perfect seasoning or cause your pan to rust. 

2. Enameled cast iron

Whole cauliflower head to be roasted in blue cast-iron pan

Even cast iron that’s enameled shouldn’t go in the dishwasher. | iStock.com/Katyenka

Think you can put your cast iron pots and pans in the dishwasher because they have a layer of enamel? Delish reports that’s not a good idea either. Although many enameled pans are technically dishwasher-safe, regular wash cycles can dull the enamel. In fact, some people find the finish even chips in the dishwasher — not the fate you want for your beloved dutch oven. 

3. Wooden utensils

Kitchen utensil set

Keep wooden utensils away from the dishwasher. | iStock.com/Svetl

Wooden spoons and spatulas get dirty, just like all the other utensils in your kitchen. But you should always wash them by hand instead of sticking them in the dishwasher. Good Housekeeping notes the water and heat are too harsh for wooden items. The combination can warp and crack your utensils. It can also dull the finish, so it’s a much better idea to keep these items out of the dishwasher. 

4. Aluminum cookware

Old metal pan

Wash aluminum cookware by hand. | iStock.com/Armastas

Another kind of cookware you should keep out of the dishwasher? Anything made of aluminum. Good Housekeeping reports that cookware made of aluminum can become discolored in the dishwasher. The same goes for disposable aluminum foil cookware. The Food Network reports even though aluminum cookware is technically dishwasher-safe, it can oxidize and fade from shiny to dull in just a single cycle. 

5. Soft plastics

new empty plastic food boxes

Think carefully before loading the machine with plastic items. | iStock.com/Magone

This one won’t surprise anybody who’s melted a favorite water bottle or plastic food storage container: You should never put items made of soft plastics in the dishwasher. Delish recommends, “If you can’t put hot liquids in it, don’t put it in the dishwasher.” Also, you should probably hand-wash items you want to reuse, such as butter and yogurt tubs or takeout containers you think would be useful. With items, such as water bottles, even if the bottle itself is dishwasher-safe, that doesn’t guarantee that the cap won’t melt. And with any plastics that are dishwasher-safe, you should always put them in the top rack. 

6. Knives

female chopping food ingredients

Try to wash your knives by hand. | iStock.com/Loooby

You can put your butter knives in the dishwasher all you want, but you should think twice about loading your sharp knives. The hot water can actually warp and damage the blade and loosen the handle. It can also dull the edge of even the sharpest chef’s knives, which makes them more difficult to control and more dangerous to use. Plus, sharp knives can nick the dishwasher rack and leave it open to rust. In other words, just set aside some time to hand-wash your knives. 

7. Colanders

fresh bow pasta top view with basil and cheese

Think twice before putting a colander in the dishwasher. | iStock.com/Olha_Afanasieva

A colander sounds like a great item to toss in the dishwasher as you clean up after dinner. But Delish warns there are several good reasons to wash this item by hand. Enameled colanders can chip, just like enameled cast iron. And metal colanders with sharp edges can shift in the dishwasher and nick the rack. That could cause the appliance’s rack to rust. 

8. Wooden cutting boards

Filet Mignon Steak on wooden board

Never put your wooden cutting boards in the appliance. | iStock.com/Lisovskaya

It’s smart to put your cutting boards in the dishwasher, especially if you’ve used them to prepare raw meat. But you should never put wooden cutting boards in the dishwasher. The combination of the heat and water can warp or crack them. So if you use them to cut raw meat in the future, you run the risk of liquids (and bacteria) getting stuck in the cracks in the wood. The Food Network recommends rinsing and hand-washing wooden cutting boards soon after you use them. But even then, don’t submerge them in water. 

9. Copper cookware

Copper pot

If you want that finish to stick around, wash your copper cookware by hand. | iStock.com/Aozora1

Do you use copper pots and pans or have a set of copper mugs for your Moscow mules? If so, you’re probably just as likely to leave them on display in your kitchen as you are to stash them away in a cabinet. Safeguard their gorgeous finish by keeping these items out of the dishwasher. Good Housekeeping reports that regular wash cycles can cause the surface of copper items to dull, so you should always wash these items by hand instead. 

10. Thermoses and travel mugs

Traveler pouring tea from thermos

Don’t put travel mugs or thermoses in the dishwasher. | iStock.com/Remains

Even if you bought a thermos or travel mug that’s specifically marked “dishwasher safe,” you should wash it by hand. Delish reports most insulated mugs have space between their inner and outer layers. Run the mug through the dishwasher enough times, and water can get trapped inside. Then, you’ll encounter a musty, moldy smell every time you drink from the mug. Your coffee will never taste the same. 

11. Vintage or painted china

Cup of tea on a blue stone background

Wash your vintage and painted china by hand. | iStock.com/Anna Pustynnikova

If you have your mother’s or grandmother’s china, you might want to think twice before putting it in the dishwasher. Good Housekeeping warns china with gold trim or hand-painted details can be damaged by the heat and the water pressure in the dishwasher. And it’s not just heirloom china that should stay out of the dishwasher either. Any delicate china that’s painted should be washed by hand, as well. 

12. Milk glass

Teacups Side by Side

Don’t wash milk glass in the machine, either. | iStock.com/LeticiaRose

Many people who love vintage kitchenware — or just gravitate toward new items that look vintage — probably have some milk glass in their kitchen. But Today warns you should always wash milk glass items by hand. That’s because this semi-opaque glass can go from white to yellow in just a few cycles in the dishwasher. 

13. Crystal

Crystal Decanter. Crystal glasses

Protect your crystal, and wash it by hand. | iStock.com/Keira01

You should never put crystal — vintage or new — in the dishwasher. The high water temperature and water pressure can leave these delicate items chipped or cracked. It can also dull the finish. And crystal that’s not securely packed into the dishwasher can rattle around and even break. Good Housekeeping notes some crystal is dishwasher-safe. But if you’re unsure, wash your glasses and punch bowl by hand instead. 

14. Gold-colored flatware

Modern gold and white place setting frames

Never put gold-toned flatware in the dishwasher. | iStock.com/MichellePatrickPhotographyLLC

Another surprising item you shouldn’t place in the dishwasher? Any flatware that’s gold-colored. Today reports that while most silver-toned flatware can go in the dishwasher without issue, you’ll definitely end up with discolored forks, knives, and spoons if you put gold-toned flatware in the dishwasher. The safest option is just to wash by hand instead. 

15. Family heirlooms

Green fresh peas

Protect your family heirlooms and wash them by hand. | iStock.com/Malyugin

Even cumbersome items that are annoying to wash by hand — your grandmother’s roasting pan or your aunt’s casserole dish — should stay out of the dishwasher. As Reader’s Digest points out, you should never put irreplaceable pieces in the appliance. You might wash it dozens of time without issue. But the one time that it rattles against something else in the dishwasher and breaks, you’ll be heartbroken. Just wash family heirlooms by hand to minimize the risk.

16. Jars with labels still on them

empty jar of jam

Don’t wash jars that still have labels or adhesive on them. | iStock.com/Kichigin

Recycling the jars from your jam, tomato sauce, or pickles is an eco-friendly move. Just make sure that you don’t damage your dishwasher in the process. Good Housekeeping reports that washing jars with the labels, or remnants of adhesive, still on them is a bad idea. Shreds of the label and pieces of adhesive can get stuck in the dishwasher’s filter. That can lead to lots of problems — and expensive repairs — in the future.  

17. Nonstick cookware

Raw pork neck meat in nonstick frying pan, spices, vegetables, olive oil.

Keep your nonstick cookware far, far away from the dishwasher. | iStock.com/ChesiireCat

Your pots and pans aren’t aluminum or copper, and they don’t have wooden handles. So they must be safe to put in the dishwasher, right? Wrong. The Food Network reports that you should never put nonstick cookware of any kind in the appliance. The nonstick coating won’t hold up well in the wash cycle. You might be able to make an exception for items specifically labeled “dishwasher-safe.” But you should still watch carefully to make sure that they aren’t getting damaged. 

18. Pressure cooker lids

High pressure aluminum cooking pot with safety cover

Wash your pressure cooker’s lid by hand. | iStock.com/Baloon111

Many of us turn to a pressure cooker when we need to get a meal on the table but don’t have hours to spend in the kitchen. But you’re going to need to take at least a little time to wash this kitchen tool by hand. That includes the pressure cooker lid. Today reports that putting the lid in the dishwasher can force food particles or detergent into the regulator or safety valves. To avoid this, you should wash by hand in soapy water, and then rinse and dry well. 

19. Cheese graters

The ingredients needed to make pasta cheese sauce

Don’t bother putting that cheese grater in the dishwasher. | iStock.com/Anna_Kurz

A cheese grater isn’t much fun to wash by hand. But, surprisingly enough, that’s a much better option than putting it in the dishwasher. The problem, according to Good Housekeeping, is that the wash cycle won’t effectively remove the shreds of cheese left in the grater. Instead, you should just use dish soap and a sponge to wash this item by hand. 

20. Printed measuring cups

Baking ingredients.

Wash that printed measuring cup by hand. | IStock.com/Karammiri

Do you use a measuring cup that’s printed instead of etched? Then, hand wash it, especially if you want to keep it around for years to come. Today reports that repeated cycles in the dishwasher can wear off the numbers on these measuring cups. That would make your favorite measuring cup pretty ineffective at measuring your ingredients. 

21. Cookware with food burnt on

Burnt Pan

Don’t expect the dishwasher to help you with cookware that has food burnt onto it. | iStock.com/Nodd

Good Housekeeping also warns against loading up the dishwasher with cookware that has food burnt onto it. Though it probably won’t hurt the cookware to run it through the dishwasher, the appliance won’t effectively remove the food remnants. If you want a better chance at removing burnt food, you’ll probably need to use some elbow grease instead of relying on the wash cycle.

Read More: Some of the Weirdest Things You Didn’t Know You Can Put in the Dishwasher