Bronze art

The use of the Bronze in Sculpture goes back to highest antiquity.

The Technique basic did not change through the centuries: after having modelled an object in Cire, one recovers it of a mixture containing Argile, one makes it cook, which empties wax, then one runs the Bronze there. It only remains to break the mould terra cotta to see appearing the object.

Still today, this artisanal technique is used with the Bénin, the Burkina Faso and in other areas of Africa, in India, etc

In the Western sculpture, the techniques deeply evolved/moved. The know-how of the founders justifies that works carry their print, beside the signature of the sculptor.

Technique

The Technique described below is resulting from the techniques and traditions from Burkina Faso

Modelling of wax

The modelling of wax is carried out with naked hands and also using tools to carve it. One can make it more or less malleable while heating it. As soon as the model has a mass so much is not very important, one carries out a core in argillaceous ground, Plâtre,… This makes it possible to prevent that withdrawals and defects appear at the time of cast of bronze. The modelling of wax makes it possible to carry out small details until a millimêtre thickness.

When the modelling of wax is carried out, he is necessary to add to it a stem of cast (1 to 2 cm in diameter) which will be cut out once cast bronze. One also adds stems of cast between the most distant parts to allow metal, at the time of run to distribute itself until the finest ends.

Preparation of the mould

In the traditional method Burkinabe, the mould is elaborate in several times. The wax model is covered with a first fine layer of clay.

After drying, several layers made up of a mixture of clay and droppings of dried ass, called banko , come to cover the first. The unit is then reinforced using metal stems and with Fil of iron when the part is of great dimension.

Drying of the mould

The preparation of the mould is a long method, because each layer of banko must be applied once the preceding layer is quite dry. A drying with the shelter of the Sun makes it possible the mould not to fissure.

Evacuation of wax and cooking of the mould

Once the mould is quite dry, it should be placed in a average Feu, while starting by heating the opening of exit (stem of cast) then while heating and emptying gradually towards the back of the mould. The wax can be recovered for a future re-use. When the mould is empty, a noise comparable with that of a cooking announces that the stage is finished.

The mould can then be cooked. For that, it should be placed in a very strong fire, during several hours to cook it, in embers. This cooking makes it possible to harden the banko , and also to burn the organic matters (of which donkey droppings) of the mould. This stage returns the mould then porous and the air will be able to circulate at the time of cast of metal.

Casting of metal

The traditional method Burkinabe of bronze casting uses various recovered metals (Bronze, tin, Cuivre, Zinc). The mixture carefully is prepared during heating and is carried to 1200 °C. At the time of the last moments of cooking, the founder adds a handle of coal on the top of the Creuset, which it removes then right before running metal.

The moulds are then laid out well right in Sable (one leaves them fire who cooked them). Fixed well between them, one pours bronze there liquidates either using an iron ladle, or directly by pouring the crucible in the opening.

Destruction of the mould and completions

Once castings carried out, it is waited until the moulds cool during a few hours, then one can destroy them to reveal the sculpture. Small lacks can be present, if the stems of castings were badly distributed, if the mould were badly built or if casting were not successful. One can then carry out the completions (to polish, file, sandpaper…).

Patinas

The Patine S require a great knowledge. The Sculpture obtained after casting is generally of color yellow, Doré. According to the effect which one wants to obtain one can apply various products for to oxidize metal. It is then necessary to heat the sculpture in a soft fire, to apply the mixtures and to let act (one hour until several days). When the color of the desired patina is reached, one stops oxidation with wax (wax for pieces of furniture).

Various products are used for the patinas, for example:

Acid nitric
Hydrochloric acid
Acid sulphuric
Permanganate of potassium

developments in the traditional technology

It is it should be noted that the sculptor Yannec Tomada with successful, since 2005, to transform the technique of manufacture of the moulds by removing the organic matter (hairs and droppings) which helps clay traditionally to box the thermal shock and allows the degasification of bronze. Formed at the beginning with the African technique with Ouagadougou by Bourahima Savadogo Baba then by Pépito Espin Anadon with the farm of the High-Boards of Saint Omer (14) and advised by the ceramists Paulettes Descamps and Frederic Régnier as well as the team of the museum of the pottery of Ger (50) it succeeded by using special clays assembled at high temperature in furnaces with Raku to free itself from the ancestral technique. It obtains thus parts hydrides or clay moulds it made body at piece-rates. (see photographs in external bond).

Internal bonds

Bronze
Alloys of copper
Bronze Age

External bonds

Technical and photographs: Ali Nikiéma, Artist bronzier of Burkina Faso.

the statuary of edition at the XIXe century

Code deontologic of the foundries of art

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