Why are my kitchen knives always dull?

posted in: Knife Care | 2

As a knifemaker and enthusiast I am always looking for opportunities to examine knives; When I’m at a friends place I often find myself in the kitchen taking a look at the contents of their knife block at some point during my visit. I regularly find these knives in a shockingly dull state! The interesting thing is: most of the people I know who own dull knives, know that their knives are dull! They either don’t have time to sharpen them or don’t know how to. The good news is that there are a few very simple measures you can take to avoid dulling your knives in the first place.

When treated equally a knife made from middle of the road steel (like most German factory knives for example) will inevitably get dull faster than a knife made from a high quality hard steel like the CPM S35VN stainless steel in our Alder 8” chefs. However any decent knife, even the aforementioned German factory-made chef’s knife, will hold an edge for a long time if treated correctly. The steel the knife is made from is far harder than anything you would normally cut; therefore the dulling effect on the cutting edge of the knife is very low. The harder the material a knife comes in contact with the faster it will dull. Avoiding contact with hard materials is the key to preventing premature dulling. There are a few places in your kitchen where a knife is likely to come in contact with something harder than itself.

sharp vs dull
The knife on the right is in a sharp state. The one on the left was used to cut food on a ceramic plate twice.

The first and worst is cutting on surfaces that are harder than a knife. Stone, glass, ceramic and porcelain are all much harder than even the best knife steels. That means countertops, baking dishes, cutting boards and plates made out of any of these are terrible surfaces to cut on! For example, ceramic is one of the most common abrasives used to shape steel; most knives are ground to shape using ceramic sanding belts! Think of your ceramic dinner plates as grinding wheels, wearing away a little more of your blade every time you cut on them. Always use a wooden or plastic cutting board!  A single cut on a ceramic plate will take a knife from hair shaving scary sharp, to noticeably less sharp. After a couple of medium pressure cuts on a hard surface obvious signs of dullness will be visible. A great quick test to check the state of a knife’s edge is to hold it under a bright light; a sharp knife will reflect no light off its cutting edge, a dull knife will exhibit a shiny line where the sharp edge should be. See the image on the left (click for large version).

Improper cleaning and storage will lead to edge damage as well.  A knife stored loose in a drawer alongside other knives and utensils will get nicks and dull spots along its edge from bumping into the other knives. Knives are all similar in hardness and can dull each other easily as a result. The same phenomenon occurs when a knife is washed in the dishwasher: drinking glasses, ceramic cups and plates, and other cutlery cause dulling by contact with the cutting edge. It is best to wash knives by hand using warm soapy water and store them where they won’t contact harder items. A knife block is the most common but many other options are available.

Another way many people dull their knives is by not using the right knife for the job. For example: a chef’s knife is designed to cut fruits, vegetables, meat and herbs. It is not designed to cut through bones, frozen foods, or open cardboard boxes. Avoid abusing your knives! Use a cleaver or a saw to cut through bones, not your chef’s knife.

A final very important aspect of maintaining your knives’ sharpness is using a “sharpening steel” frequently. When knives begin to dull it is usually a result of the sharp cutting edge rolling over, not actually being dull. A steel’s primary function is to straighten the rolled edge, allowing the rolled part to cut cleanly again. Using a steel is very simple and fast. It literally takes seconds and should be done every few days or as needed. Diligent use of a steel to maintain your knives can drastically increase time between sharpenings.

Many professional chefs (who use their knives all day long) only sharpen every couple of weeks. They achieve this by caring for their knives properly and using a steel at least once every day. In home kitchen use, a knife may see an hour of use per day, probably less. Professional chefs use their knives many times as much. Therefore, a home cook who cares for their knives properly shouldn’t need to sharpen more than every month and probably less frequently than that.

Eventually even the highest quality, best cared for knives no longer respond to steeling and cutting performance drops off. It is at this point that a real sharpening using abrasives is required. However, if you treat your knives as described you will significantly increase the time between sharpenings and decrease the difficulty of sharpening when it is required. Find further information on steeling and sharpening here.

2 Responses

  1. darelldd

    I love articles like this. Thank you for sharing!

    Guests who visit our home sometimes participate in food preparation in our kitchen. None of them maintain their own knives, and certainly they NEVER expect my knives to be actually sharp even after I mention this fact. They often speak of which department store knife sets I should consider buying because “they’re so sharp!” (at this point I’ll mention that it is like choosing which car to purchase because it has so much gas in the tank!)

    When guests use my maintained knives, even when the blade easily slips into the food being cut, the high-pressure finish into the board at the end of the cut destroys my boards! They will scrape the perpendicular blade sideways on the cutting surface to collect the cut bits of food into a pile. I have people using the boning knife to slice vegetables “because it seemed sharp.” (this generally means it was the first knife they pulled from the block). And drawing blood from a sharp tip is a regular occurance (“I knew the knife was sharp, but I couldn’t have known that the tip would be sharp too!”)

    So all of that is just a long way of asking: How do I explain to my guests what a sharp knife is, and how they should be used without sounding condescending or being “that guy?” When I begin with “my knives are sharp” they simply have no idea what sharp is, and just nod and go about doing all these things that make me cringe.

  2. Pat Conaway

    Thanks, that was a very informative article, we’ve been having a lot of discussion around keeping the kitchen knives in good order.

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