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Nerdy Science in the Kitchen

Dishwashers and Knives: The Never Again Story



multiple knives fanned out
Should you wash your knives in the dishwasher?

Let’s be honest: dishwashers are lifesavers in these modern times.

They allow us to say goodbye to the tiresome chore of hand-washing dishes and pots and pans, buying us some time to accomplish other needful tasks. Every homeowner is thankful for their dishwasher’s existence, in one way or another.

On the other hand, good knives are also one of your kitchen’s most essential tools, especially for those who love to cook. They are the core of every meal preparation, slicing, cutting, dicing, and chopping your ingredients to create perfect meals.

Since they are so important (and also often very expensive!), our kitchen knives are precious, and you should do your very best to keep them in great shape–no matter what.

So that leads us to the question: can we really wash everything in dishwashers? Are kitchen knives dishwasher-safe, or are they better off being hand-washed?

Do Dishwashers Dull Sharp Knives?

A common kitchen question we hear all the time is: do dishwashers dull already-sharp knives? And we often hear the same answer: “Never put your sharp knives in the dishwasher!” But is this good advice? Is it true you should only hand wash your kitchen knives?

The short answer is: yes. Frankly, dishwashers are harmful to good, sharp knives for three reasons.

  1. Dishwasher detergents contain harsh chemicals that are tough for the knives.
  2. Placing knives in the dishwasher with high heat and running water may pose a safety issue. Sharp knives in the dishwasher can scratch other kitchen items and can also be dangerous during the loading and unloading of the dishwasher.
  3. The dishwasher cycle can damage the knives themselves, but also can damage the coating of the racks of your dishwasher. The process also makes the knives more susceptible to rust and corrosion.

How Heat and Water Ruin Your Knives

Dishwashers work by combining high temperatures with, of course, high-pressure running water to clean dishes and pans effectively.

But when it comes to sharp knives in the dishwasher, it’s another story entirely.

The truth is, both heat and water are harmful to your good knives’ condition in various ways. High-temperature water in dishwashers can damage the knives’ stainless steel blades and handles. It also can cause the knives to warp and become deformed or bent at a certain angle, ruining them forever.

open dishwasher filled with clean glasses, silverware, and white dishes
Dishwashers are great. But not for your knives.

How Dishwasher Cycles Ruin Your Knives

If you are curious what goes on inside the dishwasher while it’s turned on, don’t buy a waterproof camera. Instead, imagine your clothes inside a washing machine. It’s basically the same process–the only difference is what’s being washed in the machine.

Any items placed in dishwashers need to be carefully arranged in the racks to avoid scratched, ruined dishes and cookware and well as to avoid damaging the coating on the racks of the machine. Imagine putting a knife in the washing machine to clean it. Do you think it will work? Well, yes, you’ll definitely have a clean knife afterward, but it’ll be in a totally different condition–a damaged one.

Additionally the high-pressure water spray in a running dishwasher will cause any sharp knives in the load to bump and bang around during the wash cycle, resulting in dulled and damaged blades. Nobody wants this happening to their well-loved knives! Plus, these same knives can scrape against delicate dishes, causing breaks and cracks, or against expensive pots and pans, scratching those delicate cooking surfaces, just another good reason to skip the dishwasher and to wash your knives by hand.

How Dishwasher Detergent Ruins Your Knives

One final component of what damages sharp knives in the dishwasher is probably something you didn’t even consider: the dishwasher detergent.

Basically, dishwasher detergents are reactive (and injurious) to several types of metals, including stainless steel and silver. It is not advisable to put your kitchen items made of these materials in your dishwasher.

Dishwasher detergents are designed to work aggressively on dirty dishes–too aggressively to work on your costly kitchen knives. These detergents may cause your best knives to lose their sharp edges, resulting in a useless knife. It’s always best to opt for a more gentle cleaning approach for good knives–hand washing.

Can Stainless Steel Knives Be Washed in the Dishwasher?

There are different techniques of knife maintenance for different steel blades. For example, a stainless steel knife is cleaned differently than a carbon steel knife. Using the wrong cleaning technique for certain blades can lead to them rusting prematurely.

Like other steel knife blade types, stainless steel knives are easy to clean because stainless steel does not oxidize. The number one rule of cleaning them, though, is never to clean them in the dishwasher. When hot water is mixed with dishwasher detergents’ chemicals, it results in stains on stainless steel knives, especially if they come in contact with silver items in the wash.

Stainless steel blades should be cleaned only with hot water and dish soap. A tip: be mindful of the dish soap you use for stainless steel knives, as harsh dish soap can damage them. Also, you should not just leave your knife to air dry. Use a clean cotton rag to dry any blades. These steps will help you best preserve the sharpness of your knife blades.

How to Correctly and Safely Wash Your Knives

Knives need be cleaned due to the fact that they are prone to accumulating bacteria. This cleaning must be done correctly.

There are two main things to keep in mind when you are ready to wash your knives correctly and safely: never wash knives in the dishwasher and never leave knives soaking in water (leaving your knives in water for any amount of time will just encourage oxidation).

Given all this, you may be wondering: what then is the best way to clean the knives? Keep reading to learn how to wash your knives the best way.

What To Use:

  • Hot water
  • Mild dish soap
  • Sponge or dishcloth


  • First things first, handle your knife with care. Keep the sharp edge of the knife pointing away from your fingers or your body.
  • Using a sponge or dishcloth with hot water and mild dish soap mixture, wipe food, dirt, and residue off of both sides of the blade. Always make sure to keep the tip of the knife pointing away from you, not toward you.
  • If dried food is stuck on the blade, soak the knife in shallow water for a minute or two. This is better than accidentally cutting yourself while trying to scrub the blade vigorously.
  • Practice a correct and safe drying process for your knives. Wipe them dry with a clean cotton cloth–don’t let them air dry.
five knives lined up on black counter in order of sizes
Washing your knives in the dishwasher is basically a big no-no. Clean and dry your blades safely and correctly using our tips

How to Correctly and Safely Dry Your Knives

Unlike other kitchen items, knives are not meant to be air dried.

The correct way to dry your kitchen knives is to wipe both sides of the blades with a clean, dry cotton rag or dish towel. This will keep your knives sharp.

Allowing your knives to stay wet can lead will either damage your knife or, at the very least, lead to its rusting–even if it’s stainless steel knife.

An additional note: make sure to also store your knives carefully and properly. Do not let them bump against other knives or any other utensils or cookware. They can be damaged or cause damage to your other kitchen items.

Other Ways You May Be Ruining Your Knives

Sharp knives are valuable and an important investment for any kitchen. We use them every time we prepare a meal: it’s just impossible to run a good kitchen without them. It’s best to know how to keep our knives in good condition for as long as we can–a lifetime, even.

Learning what might ruin a good knife is essential. Aside from placing knives in the dishwasher, here are some of the ways you may be ruining your sharp knives:

two knives on wooden cutting board on gray background
Are you using the right kind of cutting board? Some cutting boards can actually damage your expensive knives.
  • Using knives to open boxes. Yes, we have all done it. But it’s really bad for your knives. This practice will dull the blades quickly. Plus, it’s simply not sanitary! Your knife can accumulate bacteria or germs if you use them for tasks they’re not meant for.
  • Storing sharp knives in a drawer. Most of us think it is the safest place to store sharp knives, especially if we have explorative small children in the home. But a drawer is not the best place for your knives: they may damage one another from close contact, and worse, reaching carelessly in a drawer filled with knives is dangerous. Instead, find a magnetic knife strip or wooden knife block that works best for you. They’re much safer and also more convenient.
  • Scooping using the knives’ sharp edges. If you often use the sharp blade of a kitchen knife to scoop up ingredients during meal prep, your knives will get dull pretty quickly. Look for an alternative for scooping up food, such as a pastry or bench scraper.
  • Using knives on a wrong cutting board. There is actually a direct relationship between knives and cutting boards. Plastic and wood chopping boards best reduce the chance for damaging your blades, more so than stone or glass boards.
  • Using sharp knives for improper tasks. Knives are used for slicing, chopping, dicing, and cutting food–period. If you try to use it for opening packages or cutting anything other than food, you set up your knives to fail.


Dishwashers help to minimize the burdens of our day-to-day tasks. As convenient as it would be if they were, not all kitchen items can or should cleaned safely and correctly in dishwashers.

Knives are one of these items. We do all we can to preserve our knives’ sharpness and to keep them free from rust and stains. The key to achieving this is having right knowledge of proper knife maintenance.

Washing knives in the dishwasher is not ideal, to say the least. Knives need to be hand-washed using hot water and mild dish soap. Lastly, proper and safe drying using a dry cotton rag is essential to prevent rust and corrosion.

Frequently Asked Questions

Are dishwashers bad for knives?

Yes. Dishwashers can cause harm to good knives. It’s not ideal for knives to be cleaned in the dishwashers. Washing them in the dishwasher could lead to rusty, dull blades.

Even worse, the blades of your knives can scratch the interior of your dishwasher, as well as other dishes and cookware inside. If you want to prolong the lives of your well-loved knives, it’s best to hand wash them with hot water and mild dish soap and to dry them with a clean, dry dish towel.

What causes knives to dull?

Knives become dull for several reasons, the most common being washing them in dishwashers. Dishwasher cycles can cause your knives to bump and bang around in the machine, dulling their blades. Also, many dishwasher detergents are much too harsh to use for washing knives. Using your knives for other wrong tasks also dulls them. Lastly, allowing knives to air dry after cleaning will harm their blades. Knives should be wiped with a dry cotton dishcloth to complete the cleaning process.

How do you keep cutlery from tarnishing in the dishwasher?

If you have been cleaning your cutlery in the dishwasher for some time, you may notice little stains on your silverware. There are ways to prevent this from happening by following these easy steps:

  • Rinse your cutlery to remove all food debris before placing inside the dishwasher.
  • Wash your cutlery after use. Waiting too long may lead to leftover food staining your silverware.
  • Use the correct amount of dishwasher detergent. Many of us mistakenly use too much, thinking it will result in cleaner dishes, but excessive amounts of any type of soap can lead to rusting.
  • Once your machine has finished washing the dishes, remove them from your dishwasher and dry them properly if the dishwasher has not completely done so.
  • The most important thing to remember is that the more time you leave your cutlery unwashed after using, the more susceptible it will be to tarnishing.

Can stainless steel knives go in the dishwasher?

Contrary to common myth, stainless steel knives should never go in the dishwasher. The mixture of hot water and detergent chemicals can cause the steel blades to stain, especially if they’re placed together with silverware items in the cutlery section of your dishwasher.

Stainless steel knives need only hot water and mild dish soap to be thoroughly cleaned. Also, avoid letting them air dry, as that can cause the blades to rust. Instead, wipe both sides of the blades with a dry cotton rag.

Can I put my Wusthof knives in the dishwasher?

No, you should not wash your Wusthof knives in the dishwasher. It’s best to hand wash these knives using warm water and a sponge.

Two of the main reasons why Wusthof knives should not be placed in the dishwasher: it’s not entirely safe for you to unload the knives after washing, and the sharp blades can rip the interior coating of the dishwasher racks. Dishwashing these knives causes harm not only to your expensive investment, but also to your dishwasher.

What should you not put in the dishwasher?

If you value your dishes and cookware as well as your dishwasher’s life, knowing which items you should not put in the dishwasher is essential. Aside from kitchen knives, other items you should not wash in the dishwasher include cast iron, nonstick cookware, aluminum cookware, and copper cookware.

If you’re unsure about whether or not to put an item in the dishwasher, verify first if a particular kitchen item is dishwasher safe or not. It is always better to be safe than sorry when it comes to your valuable kitchen items.

Additional Resources

Kitchen Professor author
About the Author: Rhonda Richardson, Editor

Rhonda grew up with parents who gardened, hunted, fished, canned, and preserved food. Her mother was a professional cook and Rhonda credits her teaching everything from how to make homemade biscuits and gravy to what kind of meals to serve for different occasions. In the kitchen, Rhonda uses a mix of old-fashioned country cooking and up-to-date fads in the kitchen, often experimenting with replacing higher-calorie or fat ingredients with healthier options that still retain the delicious flavors of the originals.

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