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The steel bars are "cropped" into short lengths and heated in the fire. By means of the drop hammer the cropped piece is forged into its first, rough shape. With a force of up to 70 tons, the forging hammer moulds the blank into the open die on the anvil. Once the excess steel has been trimmed from the blank, and the edges cleaned, the cutlery still has to undergo a number of processes before it assumes its ultimate shape and beautiful finish.
Blades and mono-block knives are hardened in three separate stages: heating, chilling and tempering. First the knife is brought to red-heat, then it is chilled with a blast of cold air. This sudden change in temperature makes the material hard and brittle. A subsequent heating process - known as tempering - relieves the internal stress in the metal and restores the desired toughness and elasticity. Hardening is a very important work process, it is critical for cutting durability and corrosion resistance of a good blade.
Grinding and polishing
Forging and heat treatment processes leave a layer of black scale on the surfaces of the metal. This has to be removed with great care before the very costly process of manual grinding and hand polishing can begin. Any scale remaining in the pores of the metal, which are invisible to the naked eye, would eventually rust. This naturally constitutes a reason for complaint. Cutlery is polished to a smooth finish by means of rotating wheels covered with cloth or sisal, using polishing pastes. Cutlery can either be polished to a high gloss or, in a final work process, brushed to a satin finish. The greater the care that is applied to polishing, the more rust resistant stainless steel cutlery becomes.
The Egyptians called it white gold and compared it to the moon. To this day, silversmiths in Germany mark each piece of sterling with a half-moon, the symbol for silver. The history of the silversmiths trade is marked with endless rules and regulations imposed by authorities controlling silver standards. Indeed, German silverware still bears the imperial crown along with the half-moon symbol and the standard mark. The most commonly used silver alloys are marked 800 and 925. These figures denote the number of parts of fine silver for every thousand parts of material. Sterling silver is marked with the figure 925, meaning that one kilogram of silver contains925 grams of pure silver and only 75 grams of electrolytic copper, the latter giving the metal its necessary hardness. This is to all intents and purposes the best silver alloy that can be used for making silver cutlery.
The making of silver cutlery
The silver alloy is melted at approximately 1000 degrees C and cast into ingots. These are then rolled out into sheets of the required thickness. The stamping press then punches the blanks from these sheets. The blanks are then rolled to make them slightly thinner at the ends where the bowl of the spoon or the prongs of the fork will be. After careful cleaning, the blanks are placed into dies, where spoons or knife handles are then forged under a pressure of up to 300 tons. Excess metal is trimmed away and the edges are carefully smoothed. The processes of grinding and polishing with grinding belts and buffing wheels are of decisive importance for the finished quality of fine cutlery. The additional manual grinding skills of the craftsman are still required to produce cutlery of top-quality.
Knives hold a special position in the manufacture of silver and silver-plated cutlery. The blade has to be particularly strong and is therefore made of stainless steel. The handle, the knife shaft, is made of two pieces and soldered together. Knife handles of sterling silver are then dipped into a galvanizing silver bath in order to silver-plate the soldered joint. Shaft and blade are fused together with a special cement in such a way that the spigot of the blade does not loosen even after a considerable length of time. The joint is then ground and polished until it becomes invisible. After having gone through the last polishing process the knife blades are sharpened.
In principle manufacturing silver-plated cutlery follows the processes used with silver cutlery, the difference being that the material core is not silver but stainless steel. Even more rarely "Alpaka" is usedthese days. Alpaka - sometimes called nickel silver because of its brightly shining appearance - is an alloy of copper, zinc and nickel. The cutlery has to be carefully cleaned before it is silver-plated in the galvanizing bath. The thickness of the silver layer can be determined by the duration of the immersion in the bath. The most commonly used layer of silver plate is 90 grams. The figure 90/18 stamped on a coffee spoon for example tells us that 90 grams of silver are deposited on a 24 square cm cutlery surface. The figure of 18 indicates that for twelve identical coffee spoons 18 grams of silver was used. The stamp 90/3.5 on a single piece, such as a serving spoon, indicates that 3.5 grams of pure silver were used to silver-plate this piece. Rosenthal cutlery is silver-plated using the most modern processes, which make the silver coating extremely wear resistant. By virtue of a law of physics, a thicker silver coating is deposited on the exposed parts of the cutlery such as the bowls and edges of spoons, fork prongs etc., i.e. those parts that suffer particularly heavy wear and tear. It is important to the customer to be aware of this. The value of silver-plated cutlery is not determined by the amount of silver coating alone but by the overall finish such as cut and polish. Silver will oxidize, caused by sulphur- and chloride combinations found in the air and in many foods. Silver-plated and silver cutlery cannot be protected from this process. Constant use and the correct cleaning methods are the best protection.