Bronze sand casting

The Musée Rodin - Paris reopens on May 19th, 2021

Bronze sand casting


 

Extrait du PDF LCO sur la fonte au sable :

Deux procédés permettent de passer du modèle en plâtre au bronze: la fonte à la cire perdue et la fonte au sable, utilisée à l’époque de Rodin mais très rare aujourd’hui. Dans les deux cas, le bronze en fusion est coulé dans un moule autour d’un noyau qui sera ensuite retiré. Au final, l’œuvre en bronze est creuse, ce qui allège son poids et son coût. Le Normand-Romain, Antoinette, Rodin et le bronze. Catalogue des œuvres conservées au musée Rodin, Éditions du musée Rodin / Éditions de la Réunion des musées nationaux, Paris, 2007, 2 vol.; p.63

«Dans ses grandes lignes, la fonte au sable n’est pas très différente de la fonte à cire perdue. Elle est un peu plus simple toutefois car il n’y a qu’un seul moule, en sable, et pas d’épreuve en cire : cela veut dire que l’artiste n’a pas la possibilité de retoucher une dernière fois son œuvre, mais qu’il peut être assuré a priori d’une grande fidélité au modèle d’origine. Pour Rodin, qui a mis en circulation plusieurs centaines de bronzes, c’était évidemment un avantage. Le modèle, qui peut être en plâtre ou en bronze plus résistant s’il s’agit d’une édition illimitée (il est dit alors « chef-modèle »), est en général coupé pour faciliter le moulage. Le moule est réalisé en tassant du sable autour de lui. Lorsque le modèle est en plâtre, il souffre de ces opérations :"Si le modèle avait été traité par la fonte au sable, il eût été complètement morcelé, écrivait Jean Bernard dans une note du 9 décembre 1977 à propos de la fonte de La Porte de l’Enfer, chaque morceau assemblé par des coupes à la romaine, passé à la gom

 

Two processes are used to switch from plaster to bronze models: lost wax casting and sand casting, which was used in Rodin's time but is very rare today. In both cases, the molten bronze is poured into a mold around a core which is then removed. In the end, the bronze work is hollow, which lightens its weight and cost. Le Normand-Romain, Antoinette, Rodin et le bronze. Catalog des œuvres conservées au musée Rodin, Éditions du musée Rodin / Éditions de la Réunion des musées nationaux, Paris, 2007, 2 vols; p.63

"In its broad outline, sand casting is not very different from lost-wax casting. It is a little simpler, however, because there is only one mold, in sand, and no wax proof: this means that the artist does not have the possibility of retouching his work one last time, but that he can be assured a priori of a great fidelity to the original model. For Rodin, who put several hundred bronzes into circulation, this was obviously an advantage. The model, which can be in plaster or in a more resistant bronze if it is an unlimited edition (it is then called "chef-modèle"), is generally cut to facilitate the molding. The mold is made by packing sand around it. When the model is in plaster, it suffers from these operations: "If the model had been treated by sand casting, it would have been completely broken up," wrote Jean Bernard in a note dated December 9, 1977, about the casting of The Gates of Hell, "each piece assembled by Roman-style cuts, passed through shellac, which would have removed its original character of plaster. Moreover, each piece that had been subjected to the treading of the foundry clay and the cutting of the pieces would have been irreparably marked, not to say damaged, by these different operations. (With the lost wax) the model will not be altered in any way and, on the contrary, restored and strengthened, rendered in such a state that it can be exhibited." After the thickness print, the core is placed back inside this mold and the bronze cast directly. To take out the proof, the mold must be broken: it cannot be used again, but the sand can be reused. After the casting, and although the feeding network is less complex, the work of chiseling is more important than in the case of a lost wax because, the model having generally been cut, it is necessary to assemble the various parts. These cuts entailed risks of deformation and Rodin sought to avoid them: Leblanc-Barbedienne thus made him hope that it would not be necessary to make any for Les Bourgeois de Calais and Jean-René Carrière remembered having witnessed the casting "in one go" of the great Thinker, "a rare process but less rare than its success". Such castings, possible only in the case of not too complicated forms, were indeed a real feat of which the founders who were capable of it were proud."