Do Dishwashers Dull Knives? [What You Need To Know?]

Dishwashers are a staple in most homes. We use them to clean dishes, pots, and pans. But what about our knives? Can they go in the dishwasher without getting dull? Before putting your expensive knives in the dishwasher, find out whether it’s better to hand-wash them.

Do Dishwashers Dull Knives?

Knives are made of metal alloys containing iron. This material is susceptible to corrosion from water and heat. When exposing knives to these elements in the dishwasher, the metal oxidizes and causes the knives to dull. Not to mention dishwashing detergent is very abrasive, and the banging around the knives will endure during the cycle will cause nicks and chips.

All of these factors will lead to a duller blade. So how do you care for your expensive kitchen knives, and does this affect all knives, including cheap knives you’ve purchased from Walmart or Amazon?

If you must put your knives in the dishwasher, there are some things you can do to minimize the damage.

We’ll discuss this topic further so you fully understand how to keep your knives in pristine condition.

Can You Put Knives In The Dishwasher?

While there’s no law stating you can’t put knives in the dishwasher, many people, myself included, put some of our knives in the dishwasher. That said, our expensive Cutco knives never go in the dishwasher. Instead, we hand-wash them and dry them immediately after use to prevent any corrosion or dulling of the blade.

If you have cheap knives you don’t care that much about, then, by all means, put them in the dishwasher. But if you have a set of expensive knives, it’s best to hand-wash them.

That said, there are several types of kitchen knives, and not all knives are created equal. So let’s look at the different types of knives and how they hold up in the dishwasher. 

But first, let’s look at why dishwashers ruin knives.

How Dishwasher Cycles Damage Knives

Dishwashers work by spraying hot water and detergent on our dishes. The dishwasher then uses a high-pressure sprayer to rinse the dishes. Finally, the dishwasher dries the dishes using either a heating element or by venting hot air into the dishwasher.

The problem is that knives are made of metal, which is susceptible to damage from water and heat. The dishwasher cycle exposes the metal to water, humidity, moisture, and harsh detergents, which causes the metal oxidizes and causes the knives to dull overtime.

In addition, dishwashing detergent contains anionic and nonionic surfactants, which consist of potent surfactants that can cause skin irritations and ruin knives. Anionic surfactants create a lot of foam. This helps wash away oil and grease.

Nonionic surfactants emulsify oils and grease, which helps the water rinse them away. When the two properties are mixed together, they create dual-action multi-purpose cleaners that are very powerful.

And while these surfactants are excellent at cleaning our dishes, they can also be abrasive and damage the blades of our knives.

Finally, the knives sit in the basket at the bottom of the dishwasher. The water spraying during the cycle causes the knives to jostle around and bang into the other silverware. This can cause nicks and chips in the blades of our knives.

If left in the dishwasher after the cycle, the knives sit in the heat and humidity. Some dishwashers use a vent to release the hot steamy air during the rinse cycle. However, moisture remains on the dishes when the vent doesn’t open. 

Moisture is the enemy of knives because it causes the metal to rust.

What Causes Rust?

Rust occurs when iron or steel is exposed to oxygen and moisture. Combining these two elements causes a chemical reaction that creates iron oxide, which we know as rust.

Rust not only destroys the aesthetic value of our knives, but it can also make them unsafe to use. It also weakens the metal and makes it more susceptible to breaking or shattering. 

While removing rust using baking soda or potatoes is possible, it’s much easier to avoid it altogether.

Which Types Of Knives Rust Faster?

As we mentioned, there are several types of kitchen knives, and not all knives are created equal. Most all knives will rust in the dishwasher, except ceramic knives. Some will rust faster than others.

Below are the different types of knives available on the market today and whether or not they are susceptible to rust.

  • Carbon Steel Knives: Carbon steel knives consist of iron and carbon. The addition of carbon makes the steel harder, which is why these knives stay sharp longer. However, carbon steel is also more susceptible to rust than other knives.
  • Stainless Steel Knives: Stainless steel is an alloy containing a high percentage of chromium (C), giving the blade its tensile strength and hardness and increasing longevity. The addition of chromium makes the steel more resistant to rusting and staining. However, stainless steel knives are not entirely rust-proof, and the dishwasher can still damage them.
  • Ceramic Knives: Ceramic knives are made of zirconium oxide, which is a tough and durable material. Zirconium oxide is much harder than steel. Therefore ceramic knives don’t dull as quickly. However, ceramic knives are very brittle and can easily break if dropped or banged around in the dishwasher.
  • Titanium: While titanium is rarely used in knife production today, some manufacturers, such as Hampton Forge, still use them. Their Tomodachi knives are made from titanium-coated material. Pure titanium doesn’t rust as easily as iron but should still be hand-washed and dried immediately to avoid rust and corrosion.

Will The Dishwasher Ruin A Knife Handle?

Knife handles were traditionally made of bone and wood. However, today most are made of aluminum, rigid plastic, titanium, stainless steel, and composite. 

Like the blade, the handles are susceptible to rust. The dishwasher can cause wooden handles to swell and crack, and plastic handles will eventually break or warp.

How to Load Knives In The Dishwasher?

Although it’s terrible for knives, we don’t recommend it. Especially quality knives made with carbon steel. Some people like Ina Garten believe everything, including knives, can go through the dishwasher.

We know some people will still put their knives in the dishwasher because it’s easier and faster.

Here are some tips you can use to load them properly into the dishwasher to help minimize the damage.

  • Place the blade pointing down. This will prevent the knives from banging around in the dishwasher and damaging the blade. It will also prevent you from cutting yourself when unloading the dishwasher.
  • Carefully arrange the knives in the basket and ensure they have plenty of room. If possible, keep them away from silverware and other utensils in their own basket.
  • Choose the Gentle cycle. Most dishwashers have different settings, and the gentle cycle is the best option for knives. This setting lessens the time they are in the dishwasher and exposed to water and detergent.
  • Consider using the top rack. The dishes on the bottom rack and utensil basket are exposed to the most heat and water. Placing the knives on the top rack will help keep them out of the direct spray. If using the top rack, ensure the knives are the only thing on that rack.

As soon as the cycle completes, remove the knives immediately and use a towel to dry them. Never leave them sitting in the dishwasher, as this will promote rusting.

Best Way to Wash Knives

Understanding how to properly clean knives is an integral part of knife care. Proper care helps extend the life of your knives and ensures your knives are properly cleaned to avoid cross-contamination.

Hand washing is the best way to clean knives. It allows you to use mild detergents such as; Dawn and Ivory or eco-friendly options such as; Dishmate, Seventh Generation, etc. In addition, hand washing also allows you to inspect the blade for any nicks or damage.

When hand washing knives, use mild dish soap and hot water. Gently scrub the blade with a soft sponge or cloth, with the blade facing away from you. Rinse the knife with hot water and dry immediately with a clean towel.

Hardwood kitchen knife handles are the only ones that require extra care. To properly care for the handles, oil the handle with canola, mineral, or coconut oil every three to six months. This helps prevent the wood from drying out and cracking.

After you clean the handle, take a small amount of oil and rub it in with a circular motion. Wipe away any leftover oil residue with a dry towel.

How to Safely Dry and Store Your Knives

Storing your knives is just as important as washing them. Improperly stored knives can lead to damage as they bang up against other utensils and pose a hazard for anyone reaching into a drawer.

You will need a knife block or sheath to store kitchen knives properly. These methods protect the blades from damage. It also prevents accidental damage when reaching into a drawer.

Final Word

In summary, throwing the knife into the dishwasher is easier because it saves you time. However, the more often you do this, the more quickly your knife will become dull. 

Even though ceramic knives are technically safe to put in the dishwasher, it’s best to get into the habit of hand-washing knives.

This will prevent you from accidentally putting one of your carbon steel knives, which are more susceptible to rust.

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