Stop Grinding Knife Edges! Straighten Them If You Want Sharp Edges That Stay Sharp!
I guess that if I were in the business of selling mechanical or electric knife sharpeners I might be tempted to tell you to sharpen your knives frequently because that way you'll be back to buy a replacement sharpener much sooner. Of course I'd never suggest that sort of thinking goes on in corporate America's board rooms but I was intrigued recently by a product review I saw on Amazon. The product in question was an electric sharpener and if memory serves the price was about a $180.00. The reviewer was quite satisfied with the product and, in fact, so satisfied that she had purchased three of these sharpeners for her kitchen in the past seven years. Roughly $600.00 worth of sharpeners in seven years? Do you know how many knives you could have had professionally sharpened for $600.00 madam? I'd say somewhere between sixty and a hundred but enough of that because here's what I need to tell you; In a "whose toughest" contest waged between your steel knives and fruits,vegetables,meats and wooden cutting boards your steel knives win every time. Carrots and cutting boards aren't going to wear away the steel edges of your knives (at least not on any reasonable time scale) so there is little reason to grind new edges unless the edges have been utterly destroyed via some means outside their intended use (more on that at the end of this article). Carrots and cutting boards will cause those tough steel edges to "roll" though and that's the common reason knives get dull. Not because the steel edge has eroded away due to normal kitchen use.
A sharp cutting edge is almost infinitesimally thin. The hair on your head is, perhaps, fifty microns in diameter and a cutting edge is less than one micron thick at the apex of the edge..This super thinness makes the edge very susceptible to any horizontal forces that it may encounter. Our instrumentation easily proves that chopping up even one carrot on a wooden cutting surface results in a measurable decline in edge sharpness and this decline is not due to some wearing away of the steel edge but rather to a simple "bending" or rolling of the edge to the side. When the edge is rolled it presents a wider profile to what ever you are attempting to cut or slice and in the knife edge world, wider = duller. This is nothing new though. Butchers and chefs have used steels (not to be confused with today's "sharpening" steels) and barbers have used straight razor strops for centuries. What is the purpose of strops and steels? To straighten edges.
Now don't get me wrong, I only said the decline in sharpness after chopping up one carrot was "measurable" by our instrumentation. That certainly doesn't mean the knife has been rendered unusable or dull. The change in sharpness after only one carrot would be undetectable by you but what do we have after you've finished chopping up all the vegetables that will go into this evenings meal? Well, the roll will certainly be even more measurable but likely, still not a discernible difference in sharpness to you but here's where the rub begins;
Let's say we're driving a nail into a piece of wood with a hammer. The nail has started into the wood just perfectly due to our well aimed hammer strikes but then our concentration fades for just a split second and we strike the nail sufficiently off-center to cause the nail to bend to the side, So what happens if we just keep striking the nail without straightening it back up first? Yes, the same thing will happen to your knife edges. Eventually the roll can increase to the point where the edge literally folds back on itself but long before that happens you will be experiencing very dull cutting edges..
So let's have some fun here. I'm going to wager that you have rolled edges on some of your favorite knives that you don't need my instrumentation to detect but rather you can detect with just your fingernail. I'm going to post a couple of pictures here to help you with your test. We are going to try and actually hook the fingernail of our index finger on the rolled edge. The rolled edge will be on only one side of the edge normally so we may have to check both sides of the edge. Begin, as in image one, with a couple of finger tips on the side blade to stabilize your hand. Place the tip of your index fingernail against the side of the blade (like you're going to scratch it) and then slowly draw the nail down until you are at the very furthermost point of the edge (image two). This is where the severely rolled edge lives. If the roll is severe enough you will literally be able to snag or hook the tip of your fingernail on it. Sometimes the roll runs the entire extent of the edge and sometimes it exists only in a short section of it so check up and down the edge at several places if necessary.
Checking for severely rolled edges
Well, how did your knives fare? If you found a few severely rolled edges don't feel bad. These kinds of edges are found in most kitchen knife drawers and blocks. The idea is to stop the progression of the roll long before before it progresses to the point where it can be detected with a fingernail. If you own the proper tools, your knife edges can be kept straight with just a few seconds of maintenance each month and your edges will always be sharp.
One footnote to all this. In addition to rolled edges there are two other reasons knife edges become dull; Abuse and neglect. Here's a few common mistakes people make in the care and use of their knives. Never use glass cutting boards. Glass cutting boards can utterly destroy a knife edge in seconds and our sharpness testers prove it. If you cut on a glass or granite cutting surface you will be grinding a new edge on your knife. Don't allow your knives to bang against each other in a drawer, the dishwasher or the sink. That's how sections of knife edges get irreparably bent and dull.Here's a simple rule - If it is as hard or harder than the steel your knife is made of then keep your knives away from it.