The Cutting Edge: NEVER use a dull knife

By / Food / August 26th, 2015 / 6

Recently, I was fortunate enough to attend a knife sharpening seminar hosted by Zwilling J.A. Henkels atToronto’s Montecito restaurant.

The session began with a quick yet informative workshop on basic knife skills lead by Chef Jonathan Collins. An interesting point that was introduced was the fact that a sharp knife is safer than a dull knife. “When you have a dull knife,” says Chef Johnathan, “is when you have the most accidents, because you are forcing the knife into the food to make it cut. A sharp knife requires little effort to cut the food, is easier to control and cuts where intended.”

Mrinal Sharma, President of Zwilling J.A. Henckels Canada followed this with the featured sharpening session. He dispelled a few myths about knives and demonstrated the correct procedure to easily sharpen knives at home. What follows are some of the more salient points of his presentation.

Sharma explained that there are two methods to determine if your knife is sharp. For the first he used the “paper test,” in which he cut down the edge of a loosely held piece of paper. A sharp knife will easily cut down a piece of paper with little effort applied, while a dull knife will tear the paper. The second method was a little unnerving as it involved him shaving the hair on his arm. I would recommend sticking with the former method.

Contrary to popular belief, when a knife gets dull, the edge does not wear away but rather it folds over on itself. A knife-edge is microscopically thin, in fact, much thinner than a human hair. The impact of cutting causes the edge to fold over on itself. A sharp knife ‘s edge will have a “v” shape; a dull knife’s edge will be bent or folded over, resulting in a “u” shape.

Sometimes running a slightly dull knife a few times along a honing steel will straighten a “rolled” edge and temporarily bring it back to sharpness. But eventually you will need to remove the little bits of bent over steel and bring the sharp edge back. For this Sharma recommends a double sided sharpening stone.

Sharpening stones (or blocks as they are sometimes referred to) may be composed of natural or artificial stone. For this session Sharma used a synthetic block, which he finds superior to natural stone as it enables a faster sharpening time (and lasts longer than natural stone).

A good sharpening stone should have two sides: a course sharpening side, and the finer “finishing” side. Sharma recommends a wet stone treatment; this involves putting a little water on the block as lubrication. With a good block you need only apply enough water to coat the upper surface of the stone; stones of lesser quality need to be soaked.

Sharma says that the biggest mistake most people make is not applying enough pressure on the blade when sharpening a knife on a stone. He recommends about six pounds of pressure. To check if you are applying this amount, he suggests using a small kitchen scale. Basically you press the side of the knife blade against the top of the scale while applying pressure. You will be able to judge the amount of downward thrust by the measurement on the scale. When I tried this exercise, I was surprised by how much pressure you have to exert to reach six pounds of pressure on the scale.

Now for the sharpening bit. Sharma says to hold the knife with your dominant hand, and use the “heel to tip” method to sharpen the knife on a block. This involves dragging the knife blade across the block from the back end of the knife to the tip. And then back again in the opposite direction. Once you done the one side of the blade, it’s time to flip the knife over and proceed on the other side.

Note that in addition, to maintaining the correct pressure, you also need to hold the knife blade at a 15 degree angle. That’s basically the angle a match book has lying flat

The final step is to flip over the stone to the finer grit and repeat the process. “What you are doing at this stage is polishing the fine edge of the knife,” Sharma explains. During his demonstration, he did this seven times each side, but he said the number of repetitions may vary according to the quality of the knife and how dull it appears.

Once you get proficient at using a wet stone it should take no more than two or three minutes per knife. A quality knife, such as those in the Zwilling J.A. Henkels line or equivalent, will hold its edge longer and actually be easier to sharpen. Reason enough to invest in quality knives.


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