Knife 101 - Dishwasher?

I get asked whether you should put your knives in the dishwasher.  There seems to be some debate out there, but for me the answer is very clear.

That answer is NO.  Never.  Don't even think about it.  It won't clean them very well, and there are a few huge issues.

Safety

Dishwasher manufacturers know that the dishwasher is not a good option for cleaning your knives.  Consequently, they don't design them to accommodate large sharp kitchen knives.  This creates a situation where you must either place the knife in the cutlery basket tip up or tip down.  Tip up creates an obvious hazard to anyone reaching into the dishwasher with anything short of complete attention.  Tip down is only marginally safer.

Edge Retention

The cutting edge of your knife is actually an amazing blend of geometry, metallurgy and craftsmanship.  In its simplest terms the cutting edge of your knife is a wedge the tapers down to an unimaginably thin piece of steel.  The high pressure jets of water gradually can wear this edge away.  A sharp knife that has been repeatedly washed in the dishwasher will often have an edge that looks almost flaky and brittle. Additionally, many detergents can prove to be slightly corrosive and abrasive.  That isn't a huge deal to the steel at the spine of the knife where you can afford to have a little steel wear away.  The edge however is a different story.

Handle Care

The handle of your knife can also take a beating in the dishwasher depending on the material from which it was made.  Most wooden handles won't cope well with all the super hot water and aggressive cleaners.  Over time this will dry out the wood, resulting in cracks forming or the handles pulling away from the knife.  The high temperatures are also damaging to the adhesive holding the handles to the knife. So even if it's not a wood handle, it's not a good idea.