From cement copper to a copper bowl
The unusual developing process of an artistically designed object
At the start of a tedious treating process stands the cement copper, a dark earthy substance from dried mud. Laurenz Stockner obtains this raw material from the copper mine in Prettau, based in the Aurina Valley in the Dolomites, Italy, where it is still extracted according to ancient methods.
The water, flowing continuously over the metalliferous vein, is enriched with copper sulphate due to present micro organisms. The coppery water is then channelled into a long wooden chute lined with ferrous stripes. Through the chemical reaction from iron and copper sulphate, copper is precipitated. The so-called cement copper (pure copper content approx. 70%) is deposited in form of smooth mud and is dried afterwards.
The work for Stockner starts at this point. Coarse copper is gained using a smelting furnace. For this he designed, according to a medieval prototype, an ad hoc conceptualised top loader and constructed it with native slate quarry pieces and clay. Only through charcoal firing lasting several days and appropriate air supply with a blower he attains a temperature of more than 1400 degree Celsius on the inside of the furnace. The cement copper given on the charcoal melts and thus, the copper collects in the bottom part of the furnace. After that, the tapping of the coarse copper is carried out.
A further smelting process follows in another furnace. The coarse copper is heated in a graphite crucible. In the material encountered impurities are widely bound to slag through diverse add-ons. When all metal is liquidated, it is poured into heated steal ingot moulds to be formed into bars and slowly cooled down.
Now the copper is heated in the forge and the glowing bar is then bit by bit formed to a copper sheet under the forging hammer.
Only at this point can Stockner cut the round and oval basic shape from the metal sheet. Using a press, the shape of the bowl slowly evolves from the lead base, whilst the centre of the copper base is continuously recessed. Thereby the material stretches on the inside, yet on the periphery it gets to a point of compression and consequently to a reduction of the circumference. The sheet begins to arch. On the contrary to iron, copper is driven out cold, but has to be reheated from time to time to restore the elasticity of the metal.
At the end of the long process the observer is presented with a simple, completed bowl, whose shape fascinates as a result of clarity and nativeness.
The self obtained/extracted material generates with its impurities and cracks a unique surface, intensified through the alternate play of colours of orange-reddish and dark nuances. Each piece is a unicum, in which a long technical-artistic formation process comes to its end.
Laurenz Stockner has pursued a headstrong path with his cement copper bowls, which is based on sensitiveness, experience and knowledge. Owing to the transforming power of the fire emerges from a dark earthy substance at the end of human hand an elaborateness luminous shape, in which the intense devotion of its creator and his concentrated monitoring of the process are visible.