Herder chef's knife K5 HRC 60 blue pierced

The Windmill knives from Robert Herder in Solingen are justly known for their carbon steel component of at least 75% and a hardness grade of at least 56 HRC for the carbon steels. They stand out for their traditional sharpening technique: Windmill knives are sharpened to an extreme thinness. The result is an astounding cutting experience.
The most time consuming type of sharpening is the Kessel’s bulge grinding, a special kind of thin grinding in which the blade is taper sharpened from the blade to the back of the knife.

Glazing is what one calls in Solingen the smoothing out of grinding scores remaining on the blade, or the final grinding. The most time-consuming step of the glazing technique is blue glazing, whereby the steel is ground finer and finer in several stages. A blade that has been blue glazed has a slight blue hue.

The elastic blades of the following knife has received the Solingen final grinding and is blue glazed. Owing to the very high Rockwell grade (HRC) of 60 it retains its sharpness much longer.

Because of their high degree of hardness and extreme thinness due to sharpening, the blades should never be twisted or turned. Under certain circumstances this can lead to ruptures in the material.

Windmühlen knives from Robert Herder in Solingen are remarkable not only because of the knife steel (at least 0.75% carbon content and a hardness of at least 56 HRC for the carbon steels), but above all because of the craftsmanship that spares none of the traditional grinding efforts: Windmühlen knives are ground extremely thin. This results in their amazing cutting ability, which is an experience in use. The most elaborate type of grinding is the whale grind, a special type of thin grinding in which the blade is ground tapered towards the back of the knife.

In Solingen, pließten is the name given to the smoothing of the grinding grooves remaining on the blade, i.e. the fine grinding. The most complex stage of this technique is blue finishing. In this process, the steel is ground finer step by step. You can tell that a blade has been blue-peened because it reflects a slightly bluish light.

The elastic blades of Herder's blue-embossed knives are ground in the Solingen thin section as well as the fuller section. Thanks to the very high hardness of 60 Rockwell (HRC), they retain their sharpness significantly longer.

Because of the high hardness - and because they are ground so exceedingly thin - the blades should not be twisted or even tilted, as this can lead to chipping of the material when cutting under certain circumstances.

The traditional material for knife blades is carbon steel. It is not rustproof, but with a fine-grained structure it can be hardened to a particularly high degree and made extremely sharp. The higher the carbon content, the higher the hardening capacity. These knives owe their high cutting ability to the material in addition to the finish, and their high cutting edge retention to a material-related self-sharpening effect. Each time a cut is made through fruit or vegetables, a minimal amount of material is removed and the blade wears evenly. The knifemaker refers to this as micro-corrosion. In fact, this means that the blade becomes steadily narrower over the years - but always retains its sharp grinding angle. Blades made of carbon steel acquire a dark patina over time, but this in no way negatively affects their quality; on the contrary, it gives them better protection against corrosion.

Carbon steel knives do not belong in the dishwasher. Wipe the knives dry after rinsing and occasionally apply some blade oil. Discoloration may occur on the blade material. However, this is not a sign of inferior quality, but only indicates the rather high carbon content in the material. In case of flash rust, the use of the rust eraser is recommended. A resharpening can be done with the sharpening steel.