Basically title but also:
— maybe this isn’t actually true
— yes, I know the dishwasher is bad for knives
In: Other
Dishwasher detergent is full of lots of tiny crystals that bash food off of your dishes to make them clean. But lots of tiny crystals bashing into the sharp edge of your knives will literally pound them flat. It’s like washing your knives with water and thousands of tiny hammers.
The theory goes that there are two problems:
1. Knives don’t do great being wet and hot for extended periods of time. You’re supposed to wipe off the blade, use soap if necessary, then dry before putting away. Dishwashers leave the knives wet for hours, and that can cause rust over time. Also, if the knife has a wooden handle, hot steam can warp it and ruin the finish.
2. Dishwashers bang stuff around. If the knife blade is resting on something, the constant movement will dull the edge.
That said, if you have a medium-to-cheap knife with a plastic handle, and you sharpen it regularly, it’s probably fine. Or if you’re like my mom and buy a new knife set every year because the old one has become dull, it’s probably okay for you, too.
A few years ago I was on a consulting gig at a “major German knife manufacturer” and asked the same question. According to them, dishwashers aren’t inherently bad for knives nor do they dull them. Dishwashing detergent, however, can be very bad for metal (depends on the quality/composition of materials used in the knife’s construction).
It really is the detergent that’s the problem.
In addition to the abrasives knocking down the blade edge, there’s this fun metallurgical phenomenon called hydrogen embrittlement. In short, metal atoms form a web that gives it its strength and flexibility. Hydrogen atoms are small enough to fit in between metal atoms in the web, which disrupts its strength and flexibility. Dishwashing detergents have a bunch of compounds built to react with food particles, and one of the results of those reactions is a bunch of hydrogen floating around, which can and will effect the steel of your knife
Now, there’s not enough hydrogen there to make your knife brittle enough to snap, but it is enough to weaken the edge of your blade. A weak blade edge won’t get as sharp and won’t stay as sharp.
The caveat to this whole thing is having a good knife to start with; a $5 knife from Walmart probably wasn’t very sharp to begin with and you won’t notice a difference putting it through the dishwasher.
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