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16 things you thought could go in the dishwasher but actually can’t

From non-stick pans to blender blades, learn what you're actually ruining by sticking it in the dishwasher

A dishwasher can make your life much easier by freeing you from doing the dishes. But do you have a tendency to throw in everything and anything?

We’ve rounded up a long list of items that you’re secretly ruining by cleaning in your dishwasher over and over again.

Make sure your future dishwasher will clean brilliantly and be a doddle to use by picking from our list of the best dishwashers

1. Kitchen knives

While steel and ceramic knives are safe in the dishwasher, and won’t tarnish, keep them out to make sure they last longer and stay in great condition.

The dishwasher could cause the knives to dull faster than otherwise, making them far less efficient.

2. Wooden spoons and chopping boards

Anything wooden, whether spoons, boards, chopsticks or servings bowls, can’t go in the dishwasher.

Regardless of what type of wood it is, the high heat of a dishwasher can cause it to splinter and split.

Instead, wash wooden items by hand but avoid submerging them in water for a long time. A quick rinse and scrub should be fine.

3. Non-stick anything

Non-stick pans should be washed and dried by hand, as the dishwasher can wear down the non-stick surface over time.

Your next omelette could be stuck to the pan if you don’t stick to this advice.

4. Copper cookware

Stylish copper pots and pans can make for a statement piece in your kitchen, especially hung up over your cooker. But to make sure your prized cookware keeps on shining, wash it by hand.

The harshness of the dishwasher can cause any copper surfaces to dull.

5. Aluminium cookware

Only anodised aluminium is dishwasher-safe, as it has a protective layer of oxide. If it hasn’t, the harsh detergent can cause it to tarnish and turn black.

If you’re not sure, it’s better to be safe than sorry and wash by hand.

6. Cast iron (even if it’s enamelled)

All cast iron will have a layer of seasoning. This isn’t salt and pepper like you put on your food, but a protective, non-stick layer of baked-on oil which you regularly have to take care of and top up.

In the dishwasher this will be washed away, and the iron beneath will rust.

Many cast iron pots and pans have a layer of enamel to make it easier for you to take care of them. But this can wear down and dull in the dishwasher.

That means you should keep your Le Creuset out of the dishwasher if you want it to last and stay bright and vibrant for a long time.

7. Oven burners and grates

It would be great if you could clean gas hob burners and grates in the dishwasher, saving you from that chore. But they are often made of cast iron, so you should avoid it.

8. Insulated coffee mugs or water bottles

The sustained high temperature of a dishwasher could damage the vacuum seal on insulated pitchers or reusable water bottles.

This will make the insulation worse and make them not as good at keeping your drinks hot or cool.


Learn how to load your dishwasher and what’s dishwasher safe with our expert guide.


9. Sterling silver cutlery or dishes

Never wash sterling silver with stainless steel (the electrolytic action can discolour and pit the metals where items touch).

Run a rinse cycle if you’re not going to start the dishwasher immediately, as prolonged contact with food containing salt, acid or sulphide (eggs, mayonnaise and seafood) can damage the finish.

With this said, if you take all these precautions, you can use your dishwasher to clean silver. But really we think it’d just be easier by hand.

10. Some baking trays

Many people stick their baking trays in the dishwasher so they don’t have to scrub them clean. But check what yours are made of: stainless steel and anodised aluminium are fine, but cast iron or regular aluminium will need to be washed by hand.

You don’t want a load of grease in your dishwasher, as it could clog the pipes. Wait for the tray to cool and for the fat to solidify. Then you can scrape it off and put it in the bin – much better for your plumbing.

11. Your pressure cooker’s lid

While the actual pot of your pressure cooker can go in the dishwasher, never put the lid in. The high heat and water jets could damage the seal mechanism, making the actual pressure part of your pressure cooker obsolete. It could even make using your pressure cooker unsafe if the safety mechanisms are faulty.

12. Blender blades

Millo blender

Many big blender brands, such as Nutribullet, say it’s fine for the blade unit of your blender to go in the dishwasher, but we’d recommend against it.

The most common problem with blenders, according to our 2019 reliability survey, is leaking – accounting for almost a quarter of all reported faults.

This could be caused by the rubber seal being stretched or torn, meaning it can’t keep the jug or cup watertight anymore. The dishwasher’s high heat could be a cause of this.

Also, just like with kitchen knives, the dishwasher could cause blender blades to dull over time, meaning your drinks will be less smooth.

13. Milk glass

You need to be gentle with milk glass. This delicate white fine glass can easily be chipped by knocking against other plates in the wash. The dishwasher may also cause discoloration, turning it slightly yellow over time.

14. Many types of plastic

You might think that you can throw any old plastic in your dishwasher, but you need to be careful. In a hot wash, certain plastic items can warp.

For plastic food storage containers, even a small amount of warping can make putting the lid on much more difficult, or make it impossible to get airtight.

If the manufacturer says the plastic is dishwasher-safe, place it on the top rack, where the wash is more delicate. And don’t select cycles that use higher wash or dry temperatures, such as the intensive or sanitise cycle.

15. Measuring cups and jugs with printed labels

If the measurements on your measuring jug or cup are printed on, as with many Pyrex jugs, you’ll want to avoid it going in the dishwasher.

The labels will wash off over time, essentially making your measuring jug just a jug.

16. Crystal

While you can wash crystal in a dishwasher if you take all the right precautions, we’d recommend against it. Over time, abrasive detergents can mark and scar the crystal. Full-lead crystal is less dense than glass and scratches easily.

If you’re adamant, choose a very mild detergent or look for one approved for crystal or cut-glass use. Place the crystal in the top rack of the dishwasher and make sure that the glasses do not touch one another. Then use a delicate cycle, which washes at a lower temperature to protect items.

If you’re not sure what all the programs on your machine do, read our guide: dishwasher programs explained.

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