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Why it is recommended not to use a dishwasher to clean your knives.

Discussion in 'The Kitchen Knife' started by Taylor, Nov 7, 2019.

  1. Taylor

    Taylor Professional Craftsman Founding Member

    I know we've all seen the knife companies advertising that it's safe to put their knives in the dishwasher, and there's even a standard you can pay to get plastered on your knife identifying it as such (NSF), but the truth is, it's not a good idea.

    In a dishwasher, there are a few things that can damage the knife: heat, detergent, and jetted water spray.

    Heat, while it may not affect the hardness of the blade, has another effect. When heating up any material, that material will expand. Different materials expand at different rates. This can negatively affect knives in a sense that the handle material will expand greater than the steel, weakening the bond between handle and tang. The more times the knife is exposed to these forces, the greater the chance for water seeping between the joints and allowing for corrosion (remember, just because a knife is labeled as stainless, doesn't mean it won't rust. It just takes longer). Not following this advice, means that eventually the handle will pry away from the knife, and need to be fixed/replaced, and can even lead to catastrophic failure in the tang weakening it to the point of failure.

    Detergents are abrasives, mixed with a jet spray, and meant to take off food particles stuck to the whatever you're washing. The problem that occurs with knives, is that they can also damage a fine edge. This leads to increased wear, and the need to sharpen, decreasing the life of your knife.

    The jetted water sprays that are used in a dishwasher are powerful enough to move your knife. Imagine your knife bouncing around knocking into the rack and dishes. This is even more added wear to the knife, and can cause major damage to the edge of your knife. You wouldn't cut on ceramic or porcelain, so why would this be good in any other context? Again, this leads to having to sharpen more, and reduces the life of the knife.

    A side note on your knife and water. Extended exposure to water will cause any knife made out of steel to rust. There are obviously some steels that have better corrosion resistance than others, but that doesn't make the impervious to rust. It's good common practice to to dry knives right away!

    This doesn't even get into how bad heat and water can be for wood.

    The best practice for cleaning a knife is to use a mild detergent/dish soap and a sponge. Rinse the knife under water, wipe with a soapy sponge (never running the edge parallel or towards your hand or sponge), rinsing it in water, then drying with a towel. If done right after use, there's no scrubbing needed, and it only takes a couple seconds. A couple seconds now, beats minutes, if not hours later, trying to sharpen or fix the problems that can crop up.

    Thanks for reading!
     
  2. Jim

    Jim Old Curmudgeon Founding Member

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