Kunstgiesserei

In the reception of art, non-ferrous metals have until recently been subsumed under the term “bronze”. It is first since the 1980s that efforts have been made to describe materials more precisely.

Pure metals are usually combined to create alloys. A wide range of standardized alloys can be obtained on the market. The chemical composition of alloys can fluctuate quite a bit depending on the characteristic. All of the values (in percent) given here should, therefore, be understood as approximations.

The appearance of the metals can be altered to a great extent depending on how the surface is processed or treated, for example, patination. It is, therefore, difficult to attribute a characteristic appearance to a specific material. Our tours provide a descriptive idea.

 

Bronze Pure tin-bronze is used in the casting of bells or when special mechanical characteristics are required. The higher the percentage of tin, the lighter and harder the bronze – when casting bells, it is usually twenty percent. The alloy customary in art casting is GBZ 10.

Amounts in percent (GBZ 10): Cu 88 / Sn starting from 10 / other
Casting temperature: 1,050–1,250 degrees Celsius

Red Brass What is generally called “bronze” is usually red brass. This contains less tin than pure tin-bronze and is the most reasonably priced non-ferrous metal. Red brass has a yellowish to reddish color, and is easy to process, enchase, and patinate. Red bronze corresponds most closely to the composition of ancient bronzes.
Amounts in percent (RG5): Cu 86 / Sn 4.5 / Zn 5.5 / Ni 1 / Pb 1.4 / other
Casting temperature: 1,020–1,150 degrees Celsius

 

Brass is a copper-zinc alloy. The amount of zinc ranges between twenty and forty percent. Brass is reasonably priced and easy to work with – it has a relatively low melting point and flow characteristics that make it easy to cast. Its resistance to corrosion makes it a suitable metal for casting fittings and armatures. It can be extruded and pressed while warm, and processed into sheet metals and profiles.

In Indian and African brass, the metal is smelted directly in the form; a strong emission of smoke indicates that the casting temperature has been reached. When polished, brass has a yellow color. It shrinks more intensively than bronze and tears more easily when cooling.

Amounts in percent: Cu 63 / Sn 1.2 / Zn 32 / Ni 18 /other
Casting temperature: 1,000–1,120 degrees Celsius

 

Nickel Silver, also called “alpaca”, “new silver” or “paktong”, is a nickel-bronze with a cool, silvery surface. Contrary to its name, it does not contain any silver. It is very weather resistant and even sea-water resistant. It is used today above all as a material for keys.
Nickel silver was customary in the chemical industry, and in the production of instruments and fittings for ships until it was replaced by chromium nickel steel. In Art Déco it was commonly used for fittings, lamps and clocks.
Amounts in percent: Cu 66 / Zn 14 / Ni 18 / other
Casting temperature: 1,140–1,260 degrees Celsius

 

Tombak The term “tombak” is no longer common – it refers to a low-alloyed brass (and/or a mixture of bronze and brass), which we produce ourselves. Tombak is used when the raw casting is meant to have a light color and should not be either reddish or yellowish.
Amounts in percent: Cu 77 / Sn 20 / Pb 2 / Si 1
Casting temperature: 1,020–1,120 degrees Celsius

 

Aluminum is gray, shiny, easy to cast and weld, and does not weigh very much. As a result of the protective aluminum oxide, it is quite resistant and reacts only slightly to changes to the surface, such as through patination.

Aluminum seems somewhat lifeless and is thus often used when a work is supposed to be painted later. If the protective oxide layer is damaged, it becomes subject to corrosion.
Casting temperature: 660–750 degrees Celsius

 

Cast Iron Iron alloys can have extremely different characteristics, depending on the carbon content and the way in which this is crystallized in the structure. Due to the very high melting temperature, casting iron requires a sand or ceramic mold.
Casting temperature: 1,280–1,380 degrees Celsius

 

Steel 37 / Structural Steel is more elastic than cast iron and is used when the iron needs to withstand torsion. When it is “fresh”, the carbon content is reduced to 0.2 percent through the blowing-in of oxygen. In the factory, the metal is cast in blocks, pressed into profiles, or milled into plates, which, as a source material, can be cut, bent, stamped, and welded.
Casting temperature: 1,400–1,600 degrees Celsius

 

Chromium-Nickel Steel is remarkably tough and weather resistant. It is light gray and has a shiny-silvery color when polished. Processing it requires special know-how, since the steel behaves aggressively when molten. The high casting temperature presents special requirements for the outer mold.

The forms are prepared in our workshop but then cast in special facilities. As a result of the complexity of processing, the costs for a casting in chromium-nickel steel are quite high.
Casting temperature: 1,560–1,650 degrees Celsius

 

Lead is a commonly used metal and is also of cultural and historical importance. It was often used as a casting metal above all in the Baroque. 

Lead has a dark, grayish-blue color, is heavy, and deep and warm in expression. In contrast to surface-active bronze, it changes its color very little. It accumulates in the body and can easily lead to poisoning. The characteristic that it has of absorbing radiation can be one reason to use lead. Due to its low casting temperature, it can be processed without great effort. 
Casting temperature: 340–400 degrees Celsius

 

Zinc was often used in the 19th century for figural ornaments on roofs. It is a relatively inexpensive, easy to process material. Particularly at cold temperatures, it becomes extremely brittle and subject to corrosion, which is the reason why it increasingly presents a task for restorers.
Casting temperature: 480–520 degrees Celsius

 

Tin is used above all as solder along with lead. It is soft and pliable. Since it is not poisonous, it is often used in connection with food – as tin tableware in the past, today above all in tin-plated sheet metal for cans. As a result of its low melting point of 232 degrees Celsius, it is an appropriate material for casting attempts at home. A defining feature of pure tin is the so-called “cry of tin” – a characteristic crunching sound when the metal is bent.
Casting temperature: 250–290 degrees Celsius

 

Silver Blind text