Producing a Cast: from the Mold Creation to the Patina

From producing a silicone mold to casting in resin, plaster or bronze, the cast workshop techniques - Atelier de moulages du Louvre

Making
a mold

The casting
process

Creating
the patina

Casting is the faithful recreation of a work of sculpture and is the result of a long, meticulous process that involves creating a mold and then using it to produce multiple reproductions.
Making a mold
Making a mold from a physical imprint
Large sculptures and statues for interior design – Decorative art ideas - Silicone elastomer for the making of the Farnese Hercules mold
Silicone elastomer for the making of the Farnese Hercules mold
The artisans of the RMN-GP cast workshop make molds from original artworks. To proserve them, a protective layer is first applied to the entire piece. The statue caster then uses a brush to apply two layers of liquid elastomer. This membrane is made up to around one centimetre thick, depending on the volume being molded. The advantage of this material is that it is elastic, precise and easy to unmold.
Making a mold from a museum sculpture for reproduction and conservation - Creating the mold | rmn – grand palais casts
Creating the mold
Once the object is covered in its silicone membrane, all the layers of plaster coating are produced for the different parts of the mold. These hold the silicone in place when the piece is unmolded. A wooden frame support the coating and help with unmolding and the handling of the mold. Once the mold is finished, the artwork is unmolded. This is the most difficult step, as any mistake when handling could damage the original.
From producing a silicone mold to casting in resin, plaster or bronze, the cast workshop techniques - Making a mold - Unmolding
Unmolding
Making a mold from a 3D imprint
The cast workshop also puts its digital technology to use when producing 3D imprint, which have the dual advantage of avoiding direct contact with the artwork and making enlargements and reductions possible. As the definition of the surface offers less precision than silicone elastomer (a difference of 5 microns for a physical imprint versus 200 microns with the use of 3D), digital technology is only used when the original artwork is fragile or if a change in the format of the reproduction is sought.
From producing a silicone mold to casting in resin, plaster or bronze, the cast workshop techniques - Making a mold - Processing the digital imprint of <i>Pompon’s Bear</i>
Processing the digital imprint of Pompon’s Bear
The casting process
The Réunion des Musées Nationaux – Grand Palais cast workshop has some 6,000 molds used for casting in plaster, resin, terracotta and bronze. Slush casting is the most frequently used technique. Plaster is applied to the mold in thin layers, the first using just plaster, the second reinforced with oakum. A wooden or metal frame is produced to support and strengthen large pieces.
From producing a silicone mold to casting in resin, plaster or bronze, the cast workshop techniques - The casting process - Unmolding
Unmolding
When the plaster has set, the cast is removed from the mold. The piece has various “seams” from where the different parts of the mold have been joined together. These are trimmed and then made uniform with the rest of the model to ensure that no traces of the production process are visible.
The patina
From producing a silicone mold to casting in resin, plaster or bronze, the cast workshop techniques - The patina - Bronze-effect patina
Bronze-effect patina
The final step in producing a cast involves applying a patina to the raw material to create a surface effect that is as close as possible to the originals, lending it the appearance of marble, terracotta, bronze etc. as well as reproducing an the effect of the passing of time.
The RMN-GP cast workshop employs a team of expertb patinors. Creating a patina always involves a close inspection of the original to ensure that the result is as accurate as possible. The patinors work with museum curators to verify the model.
Large sculptures and statues for interior design – Decorative art ideas - Sculpture grand format
Marble-effect patina
Read a complete article on our work published in the Revue des Patrimoines.