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Knife Sharpening

Even with the hardest knife and the best possible edge retention, there comes a point where the sharpness degrades noticeably. There are a number of ways to test how a knife is still sharp, but the easiest ones are the paper cutting or tomato cutting test. When the knife is no longer able to produce a clean cut through a piece of paper or to cut the skin of a tomato, it’s time for action.

  

Many users have are resigned to the fact that their knives are dull, and believe that it’s difficult to keep them sharp. But that’s just wrong. Keeping your knives sharp all the time on a tomato-cutting level is fairly easy, if one follows a simple sharpening routine and has the right sharpening tools at hand.

Cutting with a sharp knife is so much more fun. One can illustrate the difference to a dull knife using the BESS scale, where sharpness is measured by the weight in grams of pressure needed to cut through a standardised test media. In this test, a common butter knife produces a score of 2000, a knife with a moderately worn edge 1000 and with a slightly worn edge 500, whereas someone very skilled in whetstone sharpening can produces edges that score 50 in this test. At such sharpness, one needs just 1/10th of the force for a cut than with a knife that has a slightly worn edge.

There are different types of sharpening, depending on the condition of your cutting edge:

Edge repair and restoration: for damaged or chipped edges

 

  • This usually happens when the blade hasn’t been sharpened for a long period of time and when it has been abused by cutting through hard objects or purposes other than just cutting food.

  • It requires removing larger amounts of material (thus reducing the height of the blade), to again obtain a straight and pointed edge without chips.

  • This process is called edge repair or restoration

drawing chipped edge sharpening repair to pointed tip

Edge sharpening: for rounded edges

 

  • This usually happens when the blade hasn’t been sharpened for a longer period of time and the cutting edge has been worn by abrasion, so that it’s no longer pointed.

  • It requires removing material from the sides of the edge, thus producing a new, pointed edge.

  • The amount of material to be removed depends on the degree of roundness on the edge.

drawing round worn edge sharpening to pointed tip

Edge maintenance and stropping: for rolled or bent edges

 

  • It occurs when the edge is still sharp and pointed, but has been rolled or bent, e.g. by cutting on a hard surface with some force.

  • This can happen even directly after sharpening. It means that your pointed edge is still there, but is just misaligned. If so, it will not hit the food in a 90° angle, so that the knife will feel dull.

  • Hence restoring the sharpness doesn’t require the removal of material, but just to realign and straighten the edge.

drawing rolled bent edge realign by stropping

How to repair, sharpen or maintain the edge of a knife and which devices to use is explained on the following pages:

Devices

Whetstones

Edge Maintenance

Routine

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