What makes the quality of a Damascus kitchen knife?
The correct choice of materials, the temperature control during forging and heat treatment performed optimally determine the quality of a Damascus kitchen knife.
The modern steel industry provides a variety of high-quality steels. In addition, there are data sheets for the steels with accurate information on the composition, mechanical properties, heat treatment etc. Since Damascus from 2 or more steel is forged and it takes place a mixing of properties, it is important to select the right steel for the intended use. Only then can come a very high quality. To realize the potential of the steels used, the blacksmith must have knowledge of the processes in the steel, and exercise care during the entire manufacturing process.
Does a damascus kitchen knife remain sharp forever?
The knife, which remains eternally sharp, there is not. Generally, holding a knife from non-stainless carbon steel, provided proper heat treatment, the sharpness longer, which is that it has no large chromium carbides, such as stainless steels, which contain 13% or more of chromium. These chromium carbides break in a finely ground out cutting out easily, which explains the lower life in stainless steels. Of course, the cutting efficiency depends upon the use of a knife. The sharpness is retained longer if a cutting board is used in wood.
What is meant by heat treatment?
Steel has a crystalline structure which can be changed by temperature or temperature profile in a given time. With the change of the crystalline structure and the change characteristics of the steel. The alloying elements play a pivotal role in the steel. They affect the time / temperature dependent conversion processes in the steel and decide on the achievable values.
Especially important for a kitchen knife are:
Normalize makes the steel fine-grained. Only a fine-grained steel can sand out fine, that is to obtain the prerequisite to a sharp edge.
Hardening This gives the steel its mechanical strength (hardness), this is important so that the kitchen knives stay sharp.
Tempering after hardening, the steel glass hard and would easily break under stress. By tempering the desired functional properties of hardness, tensile strength and toughness are set.
What is hardening?
By curing the mechanical resistance increases.
At a certain temperature, depending on the alloying elements, the structure of the steel changes. It forms a structure which is called austenite. One can imagine this as a rearrangement of the crystalline structure in steel. If the steel is now quenched, ie the temperature shut down in a certain time, the crystalline structure can not regress fast enough, instead created a structure that martensite is called. In this condition, the steel is tough.
How to sharpen a Damascus kitchen knife?
Never sharpen rapidly rotating grinding devices. The cutting edge is heated too much, whereby the heat treatment is ruined. Best of hand with fine Abziehsteinen e.g. Arkansas sharpening or Belgian chunks in connection with water, but this requires practice.
Inexperienced, I would recommend a ruby-sharpening steel, also making it possible to produce an excellent sharpness.
It is important to exert enough pressure to get a Burr-free cutting possible.
Is a blade of carbon steel safe when cutting food?
There are no health risks. Through contact with onions or acidic foods the blade darkens after a time slightly and gets a slight patina. This effect is completely normal and harmless to health. To avoid severe discoloration, you should clean a knife made of carbon steel immediately after cutting onions or acidic foods with warm water.
To avoid rust, you should always dry off a knife made of carbon steel carefully.
The history of damascus steel
The first occasional smelts of steel took place in Syria and Iraq around 2700 B.C. First smelts in reproducible form date back to 1400 B.C. in Anatolia. From there the knowledge spread over whole Europe within the next 1000 years. During this period many steel working techniques were invented and improved until steel products finally were superior to bronze. The gradual transition from bronze to steel required the use and perfection of very different techniques. Bronze was cast and work-hardened, whereas steel was hot-forged, quenched and tempered.
The antique smelting furnaces did not produce wrought iron in quantities and qualities that could be used directly. The gained puddle-balls were spongy, of uneven quality, and interstratified by impurities. They were forged flat, quenched, and broken into pieces. These were sorted by quality and forge-welded to bars of usable size. These bars had to be refined by subsequent folding until the steel was sufficiently homogenous. Sometimes the smiths combined these bars while forging in a manner to produce -beside the desired mechanical properties- decorative patterns, often the serpent pattern. Those blades had a prosperity between the 5th and 10th centuries A.D. The decorative pattern vanished from European Swords in the succeeding centuries, although refined steel was used. This is probably related to many different factors, changed requirements for blades are likely to be only some of them.
The wars against the Turks brought damascene steel back to central Europe. Pattern welding had a renaissance with the emersion of firearms. Still, the patterns have to be seen as a decorative elements.
In the 14th century, the controlled production of cast iron was developed. The ease of working this material caused a wide spread use of cast iron for every day products. Cast iron is not suited for edged weapons. In the 18th century, larger amounts of wrought iron could be smelted due to the development of industrial fining and decarburizing processes. The labor-intensive refined steels were replaced by mono-steel -now available in sufficient amounts and quality-.
Despite the long tradition of Damascene steel in Europe, its techniques were nearly forgotten and had to be revived in the 20th century. Important impulses came from M. Sachse and H. Denig, in America from B. Moran and others. Still there is much unknown or misunderstood about this type of steel. The most pronounced example is probably the idea of soft and hard layers in the cutting edge–a wide spread misunderstanding. Several researchers have proven that due to diffusion, carbon-equalization is complete after a few folds. The speed of carbon migration is commonly underestimated.
Text by Georg v. Tardy