WHEN IS A KNIFE SHARP?

When cutting meat, vegetables or fruit, the sharpness of the cutting tool is its most important characteristic and plays a decisive role in the evaluation of knives quality. The user of a knife will probably answer the question about satisfaction with his tool in this way or something similar: "With a sharp knife I don't have to use a lot of force when cutting and as a result I get a clean cutting surface."

We have developed sharpness testing methods with which you can determine knife sharpness objectively and comparably.

In principle, this depends on your feeling during the cutting process. Every user first assesses the sharpness of their cutting tool on the basis of a cutting process. This "perceived sharpness" of the knife depends strongly on the perception of the person wielding the knife and is thus shaped by different expectations and subjective feelings. A professional chef will apply different standards to the sharpness of his knife than a member of the hobby or household kitchen. Likewise, using a new or just re-sharpened knife for the first time will raise different expectations than using a used knife from the drawer.

We have developed sharpness testing methods that can be used to determine the sharpness of the knife based on a characteristic value.

A brand new or re-sharpened knife with its initial sharpness should give you a thrilling feeling. Who has not enjoyed the experience of using a freshly sharpened knife to cut a piece of food and feeling that the knife cuts like a hot knife through butter? If you do not experience this sensation, you are right to be disappointed. You should check whether you have also used the knife as it was intended to be used. Different knives are tailored for certain cutting applications or materials and cannot achieve their optimum effect for other tasks. A bread knife will not give you a perceived sharp cut through a carrot.

Our test methods give you sharpness characteristics that are independent of the application. In this way, you can also check whether a brand-new knife has been ground faultlessly.

The degree of tolerance for wether a knife can still be used depends on the perceived sharpness of the person wielding the knife and varies subjectively. A knife is definitely blunt if cutting requires an uncomfortable amount of force or movement. The knife is also unusable if the cutting surface on the food no longer meets your expectations: meat is frayed, the cut surface of a carrot becomes rough or the chives are crushed rather than cut.

With our sharpness testing methods, you can detect the degree of dulling and determine an objectively suitable resharpening time.

The appropriate time to resharpen a knife is not easy to determine. On the one hand, you would ideally like to work with a sharp knife all the time, but on the other hand, you shy away from the effort of a resharpening process. You certainly don't want to use the knife until it is unusable and your cutting surfaces become poor or your cutting sensation is unpleasant. But you also don't want to resharpen too often, because resharpening costs time (if you do it yourself) or money (if you have it done by a specialist company).

With our test methods you can determine an optimal resharpening point.

You can resharpen a knife yourself. To do this, you need a sharpening stone or one of the many sharpening devices or pullers on offer for the household. We do not want to evaluate the multitude of these devices on the market here. However, we would like to point out that with many sharpening methods the result of the resharpening is strongly dependent on the skill of the sharpener. Especially the large group of inexperienced "occasional sharpeners" often find it difficult to achieve a significant improvement - let alone to return the knife to its original condition. For a knife sharpening that is at least the quality of a brand-new knife, it is better to have the re-sharpening process carried out in a specialist workshop. Specialist workshops have qualified staff and suitable sharpening methods and will sharpen your knife to a new condition or better. Regardless of how you want to resharpen your knife, you can determine the appropriate resharpening time with our sharpening tests.

You can determine the appropriate resharpening time with our sharpening tests.

There are a variety of methods for assessing a blades sharpness. Often mentioned is the paper test, in which a sheet of newsprint or printing paper is held with one hand while the other hand guides the knife to make a cut through the freely hanging and otherwise untensioned paper. A blade is considered sharp if the knife can be pulled through the paper in a smooth motion, producing a smooth cut with no tears. In another arrangement, a tomato falls from a defined height onto a vertically positioned knife blade. Completely slicing the tomato in two thereby proves the sharpness of a blade. In other methods, scraping cuts to cut hair on the forearm or the abrasion of a fingernail serve as sharpness criteria. Apart from the fact that none of the methods produces a quantitatively measurable result, the obvious weaknesses lie in the blurring caused by subjective perception and the nature of the material.

We have developed objective test methods for measuring cutting edge sharpness that allow you to determine and compare the sharpness of a knife on the basis of quantitative sharpness parameters.

Cutting ability is considered to be the ability of a cutting edge to cut through a material more or less effectively at any given degree of blunting.

The initial cutting ability of an edge is also referred to as the sharpness with which the maximum possible cutting ability can be achieved with a freshly ground and honed edge. Viewed as a geometric quantity, the sharpness is the width of the cutting edge caused by the manufacturing process. Even under the finest honing conditions, micro-abrasions of the cutting edge material produce a stump that deviates geometrically from the theoretically possible geometry of a line, the theoretical sharpness.

The term "cutting edge retention" is also referred to in the literature as "tool life", "edge stability", "edge strength", "wear resistance" or "service life" and describes the ability of the edge to maintain its sharpness under given conditions up to a certain degree of blunting. It is understood as the resistance of the cutting edge to mechanical, thermal and chemical influences.

The chipping describes a special geometric characteristic of the cutting edge and is caused by the cutting material itself and/or by the grinding process. The actual use of the cutting tool can also cause the chipping of the cutting edge through wear mechanisms. In a narrower sense, chipping is also understood as roughness of the cutting edge with a special geometric shape.