Should You Ever Wash Sharp Knives In The Dishwasher?

I once had a roommate who put everything in the dishwasher, which led to the breakage of two of my fancy wine glasses. I was befuddled—who the heck picks up a light-as-a-feather, delicately stemmed wine glass and thinks "Yep, this should clank around a metal box for a while"?

Anyway, I've forgiven her (sort of). But it continued to amaze me that some people just toss everything—sharp knives included—into the dishwasher. Having recently witnessed this practice at a few friends' houses, I began to wonder if I wasn't wrong. Maybe technology had evolved, and the old no-knives-in-the-dishwasher thing was just an outdated myth. I checked in with the experts, both on the knives and dishwasher side.

"Dishwashers can absolutely dull the blades on sharp knives," Jeffrey Beck, product manager at Kenmore appliances, tells me. "Over time, powerful spray action can dull the blades, making it harder to cut food items that you bought the knife for."

So the dishwasher guy was on my side. What about knife people?

"We recommend that you do not put your knives in the dishwasher," reads Wüsthof's website, under the cleaning and care section. It goes on to say that teeeechnically, its knives are "suitable for cleaning in the dishwasher," but that the company recommends hand-washing knives to keep them from being damaged or corroded.

Both Kenmore and Wüsthof warn that putting knives in the dishwasher can also be dangerous for the person stuck unloading the washer, so if you're going to put sharp objects in there, be sure to place them blade down and clearly visible. Better yet, hand wash them, because the sharp edges of knives can knock against the dishwasher basket or rack, chipping its coating and leading to rust and corrosion.

I was two for two!

Drunk on newfound dishwasher knowledge, I wanted to know what else I should keep away from this appliance. Here are some other kitchen objects that manufacturers Kenmore and Whirlpool told me to keep out of the dishwasher:

  • Cast iron: You'll ruin the "seasoning"/coating, leaving it vulnerable to rust.
  • Crystal glasses: See my cautionary tale above.
  • Silver flatware: Mixing stainless steel and silver flatware can cause a chemical reaction which can cause damage to flatware.
  • Copper mugs: High temperatures and detergents can discolor and ruin the copper finish.
  • Wooden cutting boards/utensils: Warping and cracking can occur due to high temperatures.
  • Insulated travel mugs: High temperatures can damage the vacuum seal.
  • So there you have it. I am vindicated in my hand-washing of knives, cutting boards, cast iron, and fancy glassware. If you spent money on good knives like I did, then you'll want to spend some money for rubber gloves, too.