Stone casting

from Wikipedia, the free encyclopedia
Our Lady of stone cast with slight traces of colored paint, Salzburg, around 1410–1420 (Museum Liebieghaus , Frankfurt am Main)

Stone casting is a sculptural casting technique .

Stone casting initially means that aggregates are mixed with binding agent and water and filled into a hollow mold, thus creating a plastic work from artificial stone after demolding. Accordingly, the materials that are referred to by the term stone cast are varied. So z. B. the large, fully rounded figures of the Middle Ages, which were most likely made in a kind of stucco technique from marble powder and lime, called stone casting.

Modern stone casting uses cement as a binding agent and is also known as concrete casting , cement casting or artificial stone . The Portland cement required for modern stone casting was not discovered until 1835, and there have been artistic works using this technique since around 1910, e.g. B. by Wilhelm Lehmbruck , Bernhard Heiliger , Toni Stadler , Hans Arp or Claes Oldenburg .

Technology of modern stone casting

material

Modern stone casting consists of cement, water and aggregates, that is, sand and gravel; If required, additives (e.g. superplasticizers, setting retardants) and pigments can be added.

method

Stone castings can be made either as hollow castings or as full castings . Hollow castings are preferable to solid castings, both in terms of strength and weight reasons. A one-part or multi-part negative form, which was usually removed from a clay model beforehand, is isolated and filled with concrete of a suitable consistency . For this purpose, a dry mixture of cement and the aggregates is first prepared, to which water is added up to a water-cement ratio (w / c value) of 0.6 (0.6 kg water to 1 kg cement) after uniform mixing.

The structure of a stone casting usually consists of a fine and a coarse layer. Two methods are available for this: The use of earth-moist or soft concrete. Earth-moist concrete can just be balled by hand, while soft concrete liquefies during the ramming process. The evenly moistened coarse mixture is poured into the mold in layers about 3 cm thick and compacted by tamping or shaking. Careful compaction largely determines the quality of the concrete, i.e. H. its strength and the accuracy of the impression.

Reinforcements made of structural steel can be incorporated. After filling the concrete, the casting must be protected from drying out with damp cloths and foils. The negative form can only be removed after the concrete has fully matured, which occurs after 1 to 7 days at the earliest, depending on the type of cement. For post-processing, the cast seams have to be ground off, holes and imperfections can be repaired.

literature

Web links